Abstracts book ismn-2015

International Conference
Interaction of
Superconductivity and Magnetism
in Nanosystems
book of abstracts
2–4 September, 2015
Moscow, Russia

Title: International Conference “Interaction of Superconductivity and Magnetism
in Nanosystems”
Published on August 2015
by Multiprint (ООО ”ПКЦ АЛЬТЕКС”), Moscow, Russia
Conference web-site:
http://science.misis.ru/en/activity/nanosystem
© 2015 Multiprint
© 2015 Authors
ISBN 978-5-93121-375-0
Book contains abstracts presented at the conference in Moscow, Sep 2-4,
2015. Conference is organized by National University of Science and Technology
“MISIS”. Org. committee:
• Chairman: Prof. Konstantin Efetov, NUST “MISIS” (Russia) and Ruhr Uni-
versity Bochum (Germany)
• Vice chairman: Prof. Valery Ryazanov, NUST “MISIS” (Russia) and ISSP
RAS (Russia)
• Vice chairman: Prof. Sergei Mukhin, NUST “MISIS” (Russia)
• Karpov A.V.
• Shitov S.V.
• Ustinov A.V.
• Chernikov M.A.
• Kheyfets B.B.
• Galimzyanov T.R.
• Smirnova E.A.
• Maleeva N.A.
• Shtanskaya E.V.
• Lebedeva E.A.
• Chernykh S.V.

Program Overview2 September, room B-4
9:30 Registration of participants
10:00 Plenary Session: Collective Phenomena …
11:20 Cofee Break
11:40 Plenary Session
14:00 Lunch
15:00 High- superconductors … Superconducting Spin Valves …
↓ ↓
B-4 B-3
17:30 Cofee Break
17:40 Poster session (B-building, 2nd
loor hall)
18:45 End of conference day
3 September, room B-4
9:30 Plenary Session: Collective Phenomena …
11:30 Cofee Break
14:10 Lunch
15:10 Triplet superconductivity … Hybrid superconducting …
↓ ↓
B-4 B-3
18:20 End of conference day
4 September, room B-4
9:30 Plenary Session: Hybrid Systems …
11:20 Cofee Break
14:00 Lunch
17:00 Closing Conference
17:15 Cofee Break
17:35 Meeting with faculty and students (B-702 and B-725)
Program Overview
Program
1

 2 September,  room: B-4Plenary Session: Collective Phenomena in Quantum
Matter
 chairman: Prof. Konstantin Efetov
9:30 Registration of participants
10:00 Strange Metals, Fermion Signs and Entanglement
Jan Zaanen
Instituut Lorentz for Theoretical Physics, Leiden University, The Netherlands
Abstract: see page 60
10:40 Strongly Correlated Electrons in High Temperature Superconductors
Alvaro Ferraz
International Institute of Physics-UFRN, Brazil
11:20 Cofee Break
 chairman: Prof. Sergei Mukhin
11:40 Cascade of Phase Transitions Near Quantum Critical Point
Konstantin Efetov
Ruhr University Bochum, Germany; National University of Science and Technol-
ogy MISIS, Moscow, Russia
12:20 Time-Reversal Broken Chiral Superconducting Phase Driven by Electronic Corre-
lations in TiSe2
Dmitry Efremov
Leibniz Institute for Solid State and Materials Research, Dresden, Germany
13:00 Quasi-Fermi Liquid: a Special State of One-Dimensional Matter
Alexander Rozhkov
ITAE RAN, Moscow, Russia; MIPT, Dolgoprudnyi, Russia
13:30 Three Component Spin-Charge Superconducting Order Parameter and Pair Den-
sity Waves in Correlated Fermi Systems in a Magnetic Field
Sergei Matveenko
Landau Institute for Theoretical Physics, Moscow
14:00 Lunch
 2 September,  room: B-4
Program
2

 2 September,  room: B-4High-Temperature Superconductors
 chairman: Prof. Jan Zaanen
15:00 Efect of Van Hove Singularities on the d-Form Factor Charge Ordering in Cuprate
High-Temperature Superconductors
Pavel Volkov
Ruhr University Bochum, Germany
15:30 SnS-Andreev Spectroscopy of Fe-based Oxypnictides: Scaling of Superconducting
Parameters with �
Tatiana Kuzmicheva
Lebedev Physical Institute, Russian Academy of Sciences, 119991 Moscow, Russia;
Lomonosov Moscow State University, 119991 Moscow, Russia
16:00 Paramagnon Excitations Theory for Magnetic Properties of Layered Copper Oxide
Superconductors
Igor Larionov
National University of Science & Technology ”MISIS”, 119049, Moscow, Russia;
Kazan Federal University, 420008, Kremlevskaya, 18, Kazan, Russia
16:30 Modeling of Intrinsic Josephson Junctions in High Temperature Superconductors
Yury Shukrinov
BLTP, Joint Institute for Nuclear Research, and Dubna International University of
Nature, Society, and Man, Dubna, Russia
17:00 Charge Imbalance in a Stack of Intrinsic Josephson Junctions Under External Ra-
diation
Majed Nashaat
Department of Physics, Faculty of Science, Cairo University, Egypt
17:30 Cofee Break
Program
3

 2 September,  room: B-3Superconducting Spin-Valves
 chairman: Prof. Valery Ryazanov
15:00 Distribution of Condensate Functions in Superconducting Spin-Valves
Lenar Tagirov
Kazan Federal University, Kazan, Russia
15:40 FSF Spin-Valves: Comparison of Diferent Models
Nataliya Pugach
Skobeltsyn Institute of Nuclear Physics, MSU, Moscow
16:10 Controllable Tuning of Spin-Singlet and Spin-Triplet Currents in a Josephson Spin-
Valve
Vladimir Krasnov
Stockholm University, AlbaNova University Center, SE-10691 Stockholm, Sweden
16:50 Exchange Biasing of Diluted Ferromagnetic Alloy Films in Superconducting Spin-
Valves
Anatolie Sidorenko
D. Ghitsu Institute of Electronic Engineering and Nanotechnologies ASM,
MD2028 Kishinev, Moldova
17:30 Cofee Break
Program
4

 2 September,  B-building: Hall of 2nd
Floor
Poster Session
The poster session is going to be from 17:40 to 18.45. List of poster reports:
• Imaging Coherent Response of a Superconducting Metasurface
Alexander Averkin
National University of Science and Technology (MISIS), Leninskiy prosp. 4, 119049
Moscow, Russia
• Superconducting Proximity Efect in Multiorbital Materials with Strong Spin-Orbital Cou-
pling
Angelina Burmistrova
Lomonosov Moscow State University Skobeltsyn Institute of Nuclear Physics,
Moscow, Russian Federation; Lomonosov Moscow State University, Faculty of
Physics, Moscow, Russian Federation; Moscow State Pedagogical University,
Moscow, Russian Federation
• Novel Nb/Pd0.99Fe0.01/Nb Josephson Junction Magnetic Switches for Cryogenic Memory
Igor Golovchanskiy
National University of Science and Technology MISIS, Moscow, Russia; Moscow In-
stitute of Physics and Technology, Dolgoprudny, Moscow Region, Russia
• Anomalous Proximity Efect and More Than One Majorana Fermion
Satoshi Ikegaya
Department of Applied Physics, Hokkaido University, Sapporo 060-8628, Japan
• Dielectric Susceptibility of Magnetoelectric Thin Films with Vortex-Antivortex Dipole Pairs
Petr Karpov
Department of Theoretical Physics and Quantum Technologies, National University
of Science and Technology MISiS, Leninski avenue 4, 119049, Moscow, Russia
Floor
Program
5

• Peculiarity of Resonance Between Fluxon and Plasma Wave in One-Dimensional Parallel Array
of Josephson Junctions
Kirill Rodin
Dubna International University of Nature, Society, and Man, Dubna, Russia
• Detection of Single Abrikosov Vortex in a Microwave Superconductor Resonator
Kirill Shulga
National University of Science and Technology (MISIS), Moscow, Russia; Russian
Quantum Center, Skolkovo, Russia; Moscow Institute of Physics and Technology,
Dolgoprudny, Russia
• Electrical Conduction in YBa2Cu3O7–δ Single Crystals Under the Conditions of Anionic Or-
dering in the Cu(1) O1–δ Layers
Nikolai Sobolev
Departamento de Física and I3N, Universidade de Aveiro, Aveiro, Portugal; National
University of Science and Technology “MISiS”, Moscow, Russia
• Vortices at the Surface of a Normal Metal Coupled by Proximity Efect to a Superconductor
Vasiliy Stolyarov
Institut des Nanosciences de Paris, UPMC and CNRS-UMR 7588, Paris, France;
Moscow Institute of Physics and Technology, Dolgoprudny, Russia; Institute of Solid
State Physics RAS, Chernogolovka, Moscow region, Russia
Floor
Program
6

Matter
 chairman: Prof. Alvaro Ferraz
9:30 High- and Low Superconductivity and Superluidity in Fermi-Systems with
Repulsion
Maxim Kagan
P.L. Kapitza Institute for Physical Problems, RAS, Moscow
10:10 Geometrically Controlled Quantum Coherence and Non-Equilibrium Efects in
Nanoscopic Kondo Droplets
Dirk Morr
University of Illinois at Chicago, USA
10:50 Fluctuations of “Hidden Order” as Cooper Pairing Glue
Sergei Mukhin
Moscow Institute for Steel and Alloys, Moscow, Russia
11:30 Cofee Break
Program
7

Matter
 chairman: Prof. Lenar Tagirov
11:50 Clustering of Vortex Matter in Superconductor-Ferromagnet Metamaterials
Alexander Buzdin
University of Bordeaux, LOMA UMR-CNRS 5798, F-33405 Talence Cedex, France
12:30 Microscopic Theory of Vortex Pinning on Columnar Defects in Conventional, Chi-
ral and Ferromagnetic Superconductors
Alexander Mel’nikov
Institute for Physics of Microstructures, Russian Academy of Sciences, 603950
Nizhny Novgorod, GSP-105, Russia; Lobachevsky State University of Nizhny
Novgorod, 23 Prospekt Gagarina, 603950, Nizhny Novgorod, Russia
13:10 Long-Range Spin Signal in Mesoscopic Structures Under a Zeeman Splitting
Irina Bobkova
Institute of Solid State Physics, RAS
13:40 Fluxon Scattering as a Tool for Detection and Manipulations with Flux Qubit
States
Igor Soloviev
Lomonosov Moscow State University Skobeltsyn Institute of Nuclear Physics,
Moscow, Russia Lukin Scientiic Research Institute of Physical Problems, Ze-
lenograd, Moscow, Russia MIPT, State University, Dolgoprudniy, Russia
14:10 Lunch
Program
8

 3 September,  room: B-4Triplet Superconductivity and Current-Phase Relation
in Superconductor-Ferromagnet Systems
 chairman: Prof. Alexander Buzdin
15:10 Interference of Triplet -wave Condensates in Coupled Josephson Junctions
Andreas Moor
Ruhr-Universität Bochum, Germany
15:50 Triplet Proximity Efect in Superconducting Heterostructures with a Half-Metallic
Layer
Sergey Mironov
University Bordeaux, Talence Cedex, France; MIPT, Dolgoprudny, Russia; Insti-
tute for Physics of Microstructures RAS, Nizhny Novgorod, Russia
16:20 Observation of the Second Fourier Component in the Current-Phase Relation of
Josephson SFS Junctions
Vitaly Bolginov
ISSP RAS; MISiS
16:50 Long–Range Singlet Josephson Spin–Valve Efect in Ballistic SFS Junction
Alexey Samokhvalov
Institute for Physics of Microstructures RAS, GSP-105, Nizhny Novgorod, Russia
17:20 Superconducting Phase Domains in Thin s-layers of S-F/N-sIS Josephson Devices
Sergey Bakurskiy
Physics Department, MSU, 119991 Moscow, Russia; MIPT, Dolgoprudniy, Russia
17:50 Current Transport in SF-NFS Josephson Structures: Theory and Application
Nikolay Klenov
NIIFP, Zelenograd, Russia; Physics Department, MSU, Russia
Program
9

 3 September,  room: B-3Hybrid Superconducting Structures with Topological
Insulators
 chairman: Prof. Yasuhiro Asano
15:10 Spectroscopy of Surface Andreev Bound States in Topological Insulator / Supercon-
ductor Junctions
Alexander Golubov
Faculty of Science and Technology and MESA; Institute of Nanotechnology, Uni-
versity of Twente, Netherlands; MIPT, Dolgoprudny, Russia
15:50 Majorana Fermions in Topological Insulator — Superconductor Heterostructure in
a Magnetic Field
Ramil Akzyanov
MIPT, Dolgoprudny, Moscow Region, Russia; Institute for Theoretical and Ap-
plied Electrodynamics, Moscow, Russia; All-Russia Research Institute of Auto-
matics, Moscow, Russia
16:20 Coherent Electronic Transport in Hybrid Superconductor/Semiconductor-
Nanowire Structures
Igor Batov
Peter Gruenberg Institute, Forschungszentrum Juelich, Germany; ISSP,
Chernogolovka, Russia; MIPT, Dolgoprudny, Russia
16:50 Josephson Junction Detectors for Majorana and Dirac Fermions
Moitri Maiti
BLTP, JINR, Dubna, Russia
17:20 Peculiarities of DC-SQUIDs with Topologically Nontrivial Barrier
Ilhom Rahmonov
BLTP, Joint Institute for Nuclear Research, Dubna, Russia; Umarov Physical and
Technical Institute, Dushanbe, Tajikistan
Program
10

 4 September,  room: B-4Plenary Session: Hybrid Systems: Superconductors in
Contact with Magnetic Materials, Topological
Insulators, and Graphene
 chairman: Prof. Alexander Mel’nikov
9:30 Recent Topic in Odd-Frequency Pairing: Consequences of Bulk Odd-Frequency Su-
perconducting States
Yukio Tanaka
Department of Applied Physics, Nagoya University, Nagoya 464-8603, Japan;
Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia
10:10 Paramagnetic Response of Small Topological Superconductors
Yasuhiro Asano
Department of Applied Physics, Hokkaido University, Sapporo, 060-8628, Japan
10:50 Specular Interband Andreev Relections in Graphene
Dmitri Efetov
Massachusets Institute of Technology, Cambridge, USA
11:20 Cofee Break
Program
11

 chairman: Prof. Alexander Golubov
11:40 Doping Asymmetry of Superconductivity Coexisting with Antiferromagnetism in
Spin Fluctuation Theory
Ilya Eremin
Ruhr-Universität Bochum, Institut für Theoretische Physik, Bochum, Germany
12:20 The Microscopic Theory of a Normal and the Josephson Current in Junctions with
Multiband and Topological Superconductors
Igor Devyatov
Lomonosov Moscow State University Skobeltsyn Institute of Nuclear Physics, 1(2),
Leninskie gory, GSP-1, Moscow Russian Federation
12:50 Josephson Efect in SIFS Tunnel Junctions with Complex Barriers in Weak Link
Region
Mikhail Kupriyanov
Moscow Institute of Physics and Technology, 141700 Dolgoprudniy, Russia; Sko-
beltsyn Institute of Nuclear Physics, Lomonosov MSU, 119991 Moscow, Russia;
Institute of Physics, Kazan (Volga region) Federal University, 420008 Kazan, Rus-
sia
13:30 Crossed Surface Flat Bands in Weyl Semimetal Superconductors
Keiji Yada
Nagoya University
14:00 Lunch
Program
12

 chairman: Prof. Mikhail Kupriyanov
15:00 Prospective Applications of Superconducting and Superconducting-Ferromagnetic
Heterostructures
Igor Vernik
HYPRES, Inc., 175 Clearbrook Road, Elmsford, NY 10523, USA
15:40 Escape and Retrapping in Josephson � Junctions
Edward Goldobin
Physikalische Institut, Experimentalphysik II, University of Tübingen, Tübingen,
Germany
16:20 Superconducting Hybrids: From Sandwiches to Planar Structures
Valery Ryazanov
Institute of Solid State Physics, RAS, Chernogolovka, Moscow distr., Russia; Na-
tional University of Science and Technology ”MISiS”, Moscow, Russia
17:00 Closing Conference
17:15 Cofee Break
17:35 Meeting with faculty and graduate students of Theoretical Physics and
Quantum Technologies department (B-725) and Laboratory of Supercon-
ducting Metamaterials (B-702)
Program
13

Majorana Fermions in Topological Insulator — Superconductor
Heterostructure in a Magnetic Field
Ramil Akzyanov1,2,3
, A.L. Rakhmanov1,2,3
, A.V. Rozhkov1,2
, and A.D.
Zabolotsky4,3
1
: MIPT, Dolgoprudny, Moscow Region, Russia
2
: Institute for Theoretical and Applied Electrodynamics, Moscow, Russia
3
: All-Russia Research Institute of Automatics, Moscow, Russia
4
: Institute for Spectroscopy, Moscow, Russia
Report time: see page 10; Contact e-mail: apexgreen57@gmail.com
We investigate the superconducting proximity efect at the surface of topolog-
ical insulator in the presence of magnetic ield. It is known that Majorana fermion
exists at the vortex in topological insulator - superconductor heterostructure [1].
In the presence of large Zeeman ield a topological phase transition occurs in the
system and irst Chern number changes from 0 to 1. New phase has irst Chern
number equal to 1, however, no Majorana fermion exists at the vortex core in such
phase. In this work orbital efects of magnetic ield have been studied in detail.
It is shown that while one Majorana fermion is localized at the vortex core, the
second, exterior, Majorana fermion is localized at the distance ∗ ∼ � ��, where
�
√
ℎ
�
is magnetic length and � is the coherence length at the surface of topolog-
ical insulator. At suiciently large magnetic ield ∼ � exterior Majorana fermion
is localized near the vortex and is combined with vortex Majorana fermion into
the state with nonzero energy. Realistic setup of superconducting island placed
on the top of topological insulator has been studied. If vortex penetrates the is-
land, one Majorana fermion is localized at the vortex core while the second Majo-
rana fermion is localized at the edge of the island. We found that the energy gap
between edge Majorana fermion and the irst excited state is of the order of super-
conducting gap induced at the surface of the topological insulator if the system
parameters are optimized. Such Majorana fermion can be observed in scanning
tunneling microscope measurement.
References:
1. L. Fu and C.L. Kane, 100, 096407 (2008).
Paramagnetic Response of Small Topological Superconductors
Yasuhiro Asano and Shu-Ichiro Suzuki
Abstracts
14

Department of Applied Physics, Hokkaido University, Sapporo, 060-8628, Japan
Report time: see page 11; Contact e-mail: asano@eng.hokudai.ac.jp
The diamagnetism is an essential property of all superconductors. However,
we will show that small topological (or unconventional) superconductors can
be intrinsically paramagnetic at very low temperature by solving the quasiclas-
sical Eilenberger equation and the Maxwell equation self-consistently on two-
dimensional superconducting disks in weak magnetic ields. Because of the topo-
logically nontrivial character of the wave function, the unconventional supercon-
ductors host the zero-energy surface Andreev bound states, which always accom-
pany so-called odd-frequency Cooper pairs. The paramagnetic property of the
odd-frequency pairs explains the paramagnetic response of the disks at low tem-
perature. We also discuss efects of rough edge at the disc surface. In a d-wave su-
perconducting disc, the paramagnetic response is fragile in the presence of rough
surface because the paramagnetic odd-frequency pairs have the p-wave orbital
symmetry. On the other hand in a p-wave disc, the paramagnetic efect is ro-
bust against the surface roughness because the odd-frequency pairs have s-wave
orbital symmetry. Thus the paramagnetic response is characteristic feature of a
small spin-triplet superconductor.
References:
1. S.-I. Suzuki and Y. Asano, Phys. Rev. B 89, 184508 (2014).
2. S.-I. Suzuki and Y. Asano, Phys. Rev. B 91, in press.
Imaging Coherent Response of a Superconducting Metasurface
Alexander Averkin1
, A. Zhuravel2
, P. Jung5
, N. Maleeva1
, V. P. Koshelets3
, L. V.
Filippenko3
, A. Karpov1
, and A. V. Ustinov1,4,5
1
: National University of Science and Technology “MISIS”, Moscow, Russia
2
: B. Verkin Institute for Low Temp. Physics and Engineering, NAS of Ukraine, Kharkov,
Ukraine
3
: Kotel’nikov Institute of Radio Engineering and Electronics, Moscow Russia
4
: Russian Quantum Center (RQC), Skolkovo, Moscow region, Russia
5
: Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
Report time: see page 5; Contact e-mail: mrvar@yandex.ru
We study microwave response of the individual meta-atoms of a supercon-
ducting metasurface formed by a two-dimensional array of Superconducting
QUantum Interference Devices (SQUIDs). In our experiment, RF currents in the
Abstracts
15

metasurface are directly imaged by using Laser Scanning Microscopy (LSM) tech-
nique. We tested a sample with 21×21 SQUID array in a waveguide cavity de-
signed to achieve a uniform microwave distribution over the entire array. The
demonstrated tunability of 2D SQUID metasurface resonance frequency by ex-
ternal magnetic ield is about ��%, covering 8 − �� GHz range. The obtained
LSM images of the RF current distributions over the SQUID array conirm a high
degree of coherence of the entire metasurface.
Superconducting Phase Domains in Thin s-layers of S-F/N-sIS
Josephson Devices
Sergey Bakurskiy1,2
, A.A.Golubov2,3
, N.V.Klenov1
, M.Yu.Kupriyanov4,5
, I. I.
Soloviev4
1
: Physics Department, MSU, 119991 Moscow, Russia
2
: MIPT, Dolgoprudniy, Russia
3
: Institute for Nanotechnology, University of Twente, Netherlands
4
: Skobeltsyn Institute of Nuclear Physics, MSU, Moscow, Russia
5
: Institute of Physics, Kazan (Volga region) Federal University, Kazan, Russia
Report time: see page 9; Contact e-mail: r3zz@mail.ru
Josephson junctions containing normal (N) and ferromagnetic (F) materials in
the weak link region are currently the subject of intense research. The interest in
such structures is due to the possibility of their use as a control elements of super-
conductor memory compatible with the RSFQ logic. At present there are many
implementations of such controls. Among them, the tunnel structures containing
one ferromagnetic layer in the weak link region are of greatest interest. Anisotropy
of their properties necessary for operations is achieved in such devices by com-
plicating the structure of the weak-coupling area.
In this work we study theoretically the properties of S-F/N-sIS tunnel devices
in the frame of the quasiclassical Usadel formalism. We assume that the scale of
the structure is much less than the Josephson penetration depth. We demonstrate
that in the S-F/N-sIS device it is possible to achieve its separation into two regions
which have positive (0 segment) and negative (� segment) critical current densi-
ties. We prove by numerical calculations that this separation is accompanied by a
new phenomenon, namely the violation of a spatial uniformity of the supercon-
ductive ilm and its decomposition into domains with an order parameter phase
diference equal to π. The efect is sensitive to thickness of the s layer and widths
Abstracts
16

of F and N ilms in the direction along the sIS interface and vanishes in the limit
of thick s-electrode.
Coherent Electronic Transport in Hybrid
Superconductor/Semiconductor-Nanowire Structures
H.Y. Guenel1
, Igor Batov1,2,3
, N. Borgwardt1
, H. Hardtdegen1
, A. Winden1
, K.
Sladek1
, G. Panaitov1
, D. Gruetzmacher1
, Th. Schaepers1
1
: Peter Gruenberg Institute, Forschungszentrum Juelich, Germany
2
: ISSP, Chernogolovka, Russia
3
: MIPT, Dolgoprudny, Russia
Report time: see page 10; Contact e-mail: batov@issp.ac.ru
We have fabricated and studied symmetric and asymmetric planar Josephson
junctions based on InAs-nanowires and superconducting Nb-, Al- electrodes. At
low bias current regime, the symmetric junctions exhibited a pronounced Joseph-
son supercurrent. The critical current monotonously decreased with the magnetic
ield, which can be explained by a recently developed theoretical model for the
proximity efect in ultra-narrow Josephson junctions. The symmetric junctions
also showed clear signatures of subharmonic gap structures. At zero magnetic
ield, a Josephson coupling was found for the asymmetric Al/InAs-nanowire/Nb
junctions as well. By applying a magnetic ield above the critical ield of Al or by
raising the temperature above the critical temperature of Al the junction could
be switched to an efective single interface superconductor/nanowire structure.
In this regime, a pronounced peak in the diferential conductance was observed,
which is explained by relectionless tunneling.
References:
1. H.Y. Guenel, N. Borgwardt, I.E. Batov et al. // Nano Lett. 14, 4977 (2014).
2. H.Y. Guenel, I.E. Batov et al. // J. Appl. Phys. 112, 034316 (2012).
Long-Range Spin Signal in Mesoscopic Structures Under a
Zeeman Splitting
Irina Bobkova and A.M. Bobkov
Institute of Solid State Physics, RAS
Report time: see page 8; Contact e-mail: bobkova@issp.ac.ru
Abstracts
17

A theory of spin transport and spin detection in Zeeman-splitted supercon-
ducting ilms at low temperatures is developed. A new mechanism to create a
nonequilibrium spin signal, speciic only for Zeeman-splitted superconductors,
is proposed [1,2,3]. In the framework of this mechanism the observed spin sig-
nal is formed by the spin-independent nonequilibrium quasiparticle distribution
weighted by the spin-split DOS. The relaxation length of such a spin signal is de-
termined by the energy relaxation length and can be extremely large.
There can exist two types of signals: due to nonthermalized quasiparticle dis-
tribution and due to thermalized overheated electron distribution. They have dif-
ferent decay lengths and can be distinguished by their diferent dependencies on
the applied voltage.
The decay length of the nonthermalized signal is determined by the electron-
electron scattering rate, renormalized due to superconductivity. It depends cru-
cially on the temperature of the electron sybsystem and superconducting gap.
The decay length of the thermalized signal is determined by the electron-phonon
relaxation length and can be very large.
Applications of the theory to recent experimental data on spin relaxation in
Zeeman-splitted and exchange-splitted superconductors [4,5,6] are discussed. In
particular, it can explain the extremely high spin relaxation lengths, experimen-
tally observed in Zeeman-splitted superconductors, and their growth with the
magnetic ield and with the applied voltage.
References:
1. I.V. Bobkova and A.M. Bobkov, Pis’ma v ZhETF, 101, 124 (2015)
2. T. Krishtop, M. Houzet, J. S. Meyer, PRB 91, 121407(R) (2015)
3. M. Silaev, P. Virtanen, F.S. Bergeret, T.T. Heikkilä, PRL 114, 167002 (2015)
4. F. Hubler, M.J. Wolf, D. Beckmann, and H.v. Lohneysen, Phys. Rev. Lett.
109, 207001 (2012); C.H.L. Quay, D. Chevallier, C. Bena, M. Aprili, Nature
Phys. 9, 84 (2013)
5. M.J. Wolf, F. Hubler, S. Kolenda, H.v. Lohneysen, and D. Beckmann, Phys.
Rev. B 87, 024517 (2013)
6. M.J. Wolf, C. Surgers, G. Fisher, and D. Beckmann, Phys. Rev. B 90 (2014)
Observation of the Second Fourier Component in the
Current-Phase Relation of Josephson SFS Junctions
Vitaly Bolginov
ISSP RAS; MISiS
Report time: see page 9; Contact e-mail: bolg@issp.ac.ru
Abstracts
18

It is well known that the phase diference and the supercurrent through a
Josephson junction are connected via odd ��-periodic relation. In particular cases
the current-phase relation (CPR) is sinusoidal one but in general it may contain
higher harmonics of Fourier transformation. Josephson SFS junctions with ferro-
magnetic barrier are of great interest due to oscillation of its critical current vs.
barrier width caused by spin antagonism of ferromagnetism and superconduc-
tivity. The F-barrier width increasing causes periodic change of critical current
sign, or more exactly, the change of the irst CPR Fourier component sign. At
node points (� − � transitions) the amplitude of the irst CPR component turns to
zero that enables an observation of higher Fourier components. For example, in
the node point one may observe such amazing efect as half periodic CPR due to
domination of the second Fourier component.
Here I report a series of experiments that undoubtedly demonstrates the sec-
ond CPR component manifestations. We studied Nb–CuNi–Nb SFS-sandwiches
with 53 at. % Ni content in the CuNi interlayer. We’ve observed that at node point
(about 7 nm of the F-barrier width) the critical current temperature dependence
has shown a reentrant behavior with nonzero critical current at the �−� transition
temperature. At this temperature one may observe half-integer Shapiro steps ap-
pearance under inluence of ac-signal. Measurements of critical current vs. mag-
netic ield curves have shown that the sample is uniform and the efect is not due
to the junction separation into 0- and �-state regions. Moreover at the transition
temperature we could observe half-periodic Fraunhopher pattern that conirms
domination of the second CPR Fourier component. Also we have carried out a
direct measurement of the current-phase relation and demonstrated directly the
presence and domination of the second component in it. Some theoretical models
will be given to discuss unexpectedly high value of the second harmonic ampli-
tude.
Superconducting Proximity Efect in Multiorbital Materials with
Strong Spin-Orbital Coupling
Angelina Burmistrova1,2,3
, I.A. Devyatov1
1
: Lomonosov Moscow State University Skobeltsyn Institute of Nuclear Physics, Moscow,
Russian Federation
2
: Lomonosov Moscow State University, Faculty of Physics, Moscow, Russian Federation
3
: Moscow State Pedagogical University, Moscow, Russian Federation
Report time: see page 5; Contact e-mail: burangelina@yandex.ru
Abstracts
19

New microscopic tight-binding model for calculation of charge transport in
heterostructures containing unusual multiband materials is proposed which al-
lows to take into account multiband Fermi surface, the nonparabolic excitation
spectrum of the considered materials and also interband and intervalley scattering
at the boundaries. This tight-binding approach has been applied to the investiga-
tion of the proximity efect in heterostructures, containing materials with strong
spin-orbit interaction and topological insulators (2D and 3D strained HgTe). In-
duced superconducting order parameter in this material should not be treated
the same as in the single-band metal due to its essentially multiband structure
and the existence of the strong spin-orbital coupling. Taking into account mul-
tiorbital structure and complex non-parabolic excitation spectrum in such inter-
esting materials we have calculated the induced by usual s-wave superconductor
excitation spectrum in them and have obtained the efective 2D Hamiltonian. The
calculations of the normal and Josephson current in structures containing metals
with strong spin-orbit interaction were performed using the obtained efective 2D
Hamiltonian.
Clustering of Vortex Matter in Superconductor-Ferromagnet
Metamaterials
Alexander Buzdina
, A. Bespalova
, A. Mel’nikovb
a
: University of Bordeaux, LOMA UMR-CNRS 5798, F-33405 Talence Cedex, France
b
: Institute for Physics of Microstructures RAS, and Lobachevsky State University, 603950
Nizhny Novgorod, Russia
Report time: see page 8; Contact e-mail: alexandre.bouzdine@u-bordeaux.fr
Metamaterials combining superconducting (S) and ferromagnetic (F) com-
pounds permit to attend new functionalities and reveal unusual counterintuitive
efects. We show that the SF superlattices may display a very special electrody-
namics due to the nonlocal polarization of the magnetic subsystem, making the
intervortex interaction attractive at some distances [1]. These SF superlattices vio-
late the standard classiication scheme based on the Ginzburg-Landau parameter
κ the type-I and type-II superconductors correspond to � � ��√� and � � ��√�,
respectively. In the SF superlattices the vortex matter can be arranged in clus-
ters forming, thus, an intermediate state with alternating vortex and Meissner
phases. The physics of these clustering phenomenon is related to the modiica-
tion of the intervortex interaction due to the nonlocal polarization of the magnetic
subsystem. Tuning the parameters of the F and S subsystems one can engineer the
Abstracts
20

phase diagram of the vortex matter in SF superlattices. Our study permits to pro-
vide concrete recommendations for the proper choice of parameters for such S/F
metamaterials.
Fig. 1
References:
1. Bespalov, A. A., Mel’nikov, A. S. and Buzdin, A. I., EPL v. 110 (2015) 37003.
The Microscopic Theory of a Normal and the Josephson Current
in Junctions with Multiband and Topological Superconductors
Igor Devyatov1
and A.V. Burmistrova1,2
1
: Lomonosov Moscow State University Skobeltsyn Institute of Nuclear Physics, 1(2),
Leninskie gory, GSP-1, Moscow Russian Federation
2
: Moscow State Pedagogical University, Moscow Russian Federation
Report time: see page 12; Contact e-mail: igor-devyatov@yandex.ru
We present a new microscopic tight-binding approach for calculation of charge
transport in junctions with multiband and topological superconductors [1,2]. Our
approach takes into account the complex excitation spectrum of these supercon-
ductors, their multiband Fermi surface, the anisotropy of the superconducting
order parameter as well as interband and intervalley scattering at the boundaries.
This theory has been applied to calculations of a normal and the Josephson current
in diferent structures contained multiband Fe-based superconductors (FeBS). We
have considered theoretically normal metal - FeBS (N-S�) junctions, FeBS break
junctions and contacts between usual single-band s-wave superconductor and
FeBS (S-S� junctions). We have demonstrated that investigation of current-voltage
characteristics of N-S� junctions and FeBS break junctions provides the possibility
to distinguish possible ++ and +− symmetries of the order parameter in FeBS. We
also have calculated phase dependencies of the Josephson current and tempera-
ture dependencies of critical Josephson current across S-S� junctions for diferent
Abstracts
21

directions of current relative to the crystallographic axes of FeBS and diferent
lengths of an insulator layer. We have demonstrated, that the investigation of
current-phase dependencies of S-S� Josephson junctions also allows to distinguish
possible symmetries of the order parameter in FeBS [3,4]. We have conirmed mi-
croscopically the recently proposed experimental scheme to determine the sym-
metry of the order parameter in FeBS [5], and suggest a new experimental scheme
based on measurement of an amplitude of the second harmonic of phase depen-
dence of the Josephson current in diferent directions relative to crystallographic
axes of FeBS.
The proposed approach [1,2] can be applied for microscopic calculations of
a normal and the Josephson current across junctions with other new uncon-
ventional superconductors, such as Sr2RuO4, doped superconducting insulators
CuxBi2Se3 because they are also multiorbital metals. Also we demonstrate the
application of our approach to calculations of the proximity efect in contacts be-
tween usual s-wave superconductor and 3D topological insulator, taking into ac-
count its orbital degrees of freedom.
The work is supported by the RFBR, Grants № 13-02-0185, 14-02-31366-mol_a,
15-52-50054 and by the Ministry of Education and Science of the Russian Federa-
tion, Grant № 14Y26.31.0007.
References:
1. A. V. Burmistrova, I. A. Devyatov, JETP Lett. 95, 239 (2012).
2. A. V. Burmistrova, I. A. Devyatov, A.A. Golubov, K. Yada and Y. Tanaka, J.
Phys. Soc. Jpn. 82, 034716 (2013).
3. A. V. Burmistrova, I. A. Devyatov, EPL (Europhysics Letters), 107, 67006,
(2014).
4. A. V. Burmistrova, I. A. Devyatov, A. A. Golubov et. al, Phys. Rev. B, 214501,
(2015).
5. A. A. Golubov and I. I. Mazin, Appl. Phys. Lett., 102, 032601 (2013).
Specular Interband Andreev Relections in Graphene
Dmitri Efetov
Massachusets Institute of Technology, Cambridge, USA
Report time: see page 11; Contact e-mail: defetov@gmail.com
Electrons incident from a normal metal onto a superconductor are relected
back as holes — a process called Andreev relection. In a normal metal where
the Fermi energy is much larger than a typical superconducting gap, the relected
hole retraces the path taken by the incident electron. In graphene with ultra low
Abstracts
22

disorder, however, the Fermi energy can be tuned to be smaller than the supercon-
ducting gap. In this unusual limit, the holes are expected to be relected specularly
at the superconductor-graphene interface due to the onset of interband Andreev
processes, where the efective mass of the relected holes change sign. Here we
present measurements of gate modulated Andreev relections across the low dis-
order van der Waals interface formed between graphene and the superconducting
NbSe2. We ind that the conductance across the graphene-superconductor inter-
face exhibits a characteristic suppression when the Fermi energy is tuned to val-
ues smaller than the superconducting gap, a hallmark for the transition between
intraband retro- and interband specular- Andreev relections.
Cascade of Phase Transitions Near Quantum Critical Point
Konstantin Efetov
Ruhr University Bochum, Germany; National University of Science and Technology
MISIS, Moscow, Russia
Report time: see page 2; Contact e-mail: Konstantin.B.Efetov@ruhr-uni-bochum.de
In the standard picture of a quantum phase transition, a single quantum crit-
ical point separates the phases at zero temperature. Here we show that the two-
dimensional case is considerably more complex. Instead of the single point sep-
arating the antiferromagnet from the normal metal, we have discovered a broad
region between these two phases where the magnetic order is destroyed but com-
pletely diferent phases arise. Depending on parameters characterizing the Fermi
surface, one obtains a nematic state followed by a charge density wave (CDW),
superconductivity and a broad region with strong luctuations where the CDW
competes with supercondcutivity. Both the superconductivity and CDW have
the d-wave symmetry. In the situation when the transition temperature of the
nematic state exceeds the transition temperatures into the other states, the mod-
ulation vector of CDW is directed along the directions of the nematicity and is
incommensurate with the spin modulation of the parent antiferromagnet. In the
most important case of CuO lattice of high superconducting cuprates, this cor-
responds to a charge modulation on the � atoms along the bonds. The strong
competition between the superconductivity and CDW can destroy the long range
order of both the phases and this may explain the pseudogap state in the cuprates.
At lower temperatures, the luctuations are less essential and superconductivity
becomes stable. Applying a magnetic ield destroys the superconductivity but
stabilizes CDW.
Abstracts
23

The results of our theory can serve as explanation of recent experiments on
cuprates performed with the help of STM, NMR, hard and resonant soft X-ray
scattering, sound propagation, and with some other techniques.
Time-Reversal Broken Chiral Superconducting Phase Driven by
Electronic Correlations in TiSe2
Dmitry Efremov
Leibniz Institute for Solid State and Materials Research, Dresden, Germany
Report time: see page 2; Contact e-mail: d.efremov@ifw-dresden.de
TiSe2 is a quasi-two dimensional material which hosts CDW and supercon-
ducting orders. Motivated by recent progress on single-layer transition metal
dichalcogenides, we study the efects of electronic correlations in single-layer
TiSe2. We use renormalization group (RG) analysis to ind low energy couplings
and possible long range orders. Our results suggest that TiSe2 shows competition
between charge density wave (CDW) order competes with two forms of super-
conductivity, both unconventional. One possibility is s+- order analogous to the
pnictides. The second is chiral superconductivity, with possible + symmetry.
Doping Asymmetry of Superconductivity Coexisting with
Antiferromagnetism in Spin Fluctuation Theory
Ilya Eremin
Ruhr-Universität Bochum, Institut für Theoretische Physik, Bochum, Germany
Report time: see page 12; Contact e-mail: Ilya.Eremin@ruhr-uni-bochum.de
We generalize the theory of Cooper-pairing by spin excitations in the metal-
lic antiferromagnetic state to include situations with electron and/or hole pock-
ets. We show that Cooper-pairing arises from transverse spin waves and from
gapped longitudinal spin luctuations of comparable strength. However, each
of these interactions, projected on a particular symmetry of the superconducting
gap, acts primarily within one type of pocket. We ind a nodeless �− � -wave
state is supported primarily by the longitudinal luctuations on the electron pock-
ets, and both transverse and longitudinal luctuations support nodal �− � -wave
Abstracts
24

symmetry on the hole pockets. Our results may be relevant to the asymmetry of
the AF/SC coexistence state in the cuprate phase diagram.
Strongly Correlated Electrons in High Temperature
Superconductors
Alvaro Ferraz
International Institute of Physics-UFRN, Brazil
Report time: see page 2; Contact e-mail: aferraz.iccmp@gmail.com
We present an overview of the ield- theoretical renormalization group ap-
proach for the normal phase of the optimally doped cuprates. Earlier calculations
predicted sucessfully the existence of d-wave charge instabilities (d-CDW) which
were later veriied in several experiments in non-Lanthanum-based compounds.
However the reasons for the onset of the so-called pseudogap phase remains an
open problem. We discuss possible solutions for this riddle.
Escape and Retrapping in Josephson � Junctions
Edward Goldobin1
, M. Weides2
, R. Mendito1
, B. Neumeier1
, D. Koelle1
, R.
Kleiner1
1
: Physikalische Institut, Experimentalphysik II, University of Tübingen, Germany
2
: Karlsruhe Institute of Technology, Karlsruhe, Germany
Report time: see page 13; Contact e-mail: gold@uni-tuebingen.de
Recently, our group has demonstrated experimentally [1] the irst � Josephson
junction (JJ) based on a superconducting-insulator-ferromagnet-superconductor
(SIFS) heterostructure with tailored F-layer. Such a � JJ has very unusual prop-
erties [2], e.g., a �� periodic double-well energy proile, which leads to a dou-
bly degenerate ground state with the phases −� and +�, two critical currents ±
and non-trivial retrapping dynamics expected [3]. The irst potential applications
were demonstrated, e.g., a memory cell [4]. In this talk I will describe our recent
experiments with ±� JJs.
First, we investigated the retrapping of the phase in SIFS � JJs [5]. By mea-
suring the switching current histograms, we able to calculate the probability of
the phase to be trapped in −� and +� wells when the junction returns from non-
zero- to zero-voltage-state. We show that, similar to the theoretical prediction [3],
Abstracts
25

at high temperature the retrapping is deterministic (always in the +� well), while
at lower temperature we observe an onset of the butterly efect with an oscillat-
ing probability of trapping in a particular well. Unexpectedly, the probability of
trapping in a particular well saturates at a value diferent than 50% at low tem-
peratures.
Second, we investigated the escape of the phase in artiicial � JJs, made us-
ing conventional Nb–AlOx –Nb JJ equipped with tiny current injectors to create a
phase discontinuity � ∼ �. We have measured the switching current histograms
in a wide temperature range from 1K down to 20mK. Each histogram, in general,
exhibits two escape peaks corresponding to critical currents ±, having the width
�±. The dependences �±( ) stop decreasing below some temperature, which is in-
terpreted as macroscopic quantum tunneling (MQT) of the phase. To our knowl-
edge, this is the irst experimental observation of MQT in � JJ.
References:
1. H. Sickinger, A. Lipman, M. Weides, R. G. Mints, H. Kohlstedt, D. Koelle, R.
Kleiner, E. Goldobin, “Experimental evidence of a � Josephson junction”,
Phys. Rev. Lett. 109, 107002 (2012). DOI:10.1103/PhysRevLett.109.107002
2. E. Goldobin, D. Koelle, R. Kleiner and A. Buzdin, “Josephson junctions with
second harmonic in the current-phase relation: properties of � junctions”,
Phys. Rev. B 76, 224523 (2007). DOI:10.1103/PhysRevB.76.224523
3. E. Goldobin, R. Kleiner, D. Koelle, R.G. Mints, “Phase Retrapping in a Point-
like � Josephson Junction: The Buttery Efect”, Phys. Rev. Lett. 111, 057004
(2013). DOI:10.1103/PhysRevLett.111.057004
4. E. Goldobin, H. Sickinger, M. Weides, N. Ruppelt, H. Kohlstedt, R. Kleiner,
and D. Koelle, “Memory cell based on a � Josephson junction”, Appl. Phys.
Lett. 102, 242602 (2013). DOI:10.1063/1.4811752
5. submitted to Phys. Rev. Lett. (June 2015)
Novel Nb/Pd0.99Fe0.01/Nb Josephson Junction Magnetic Switches
for Cryogenic Memory
Igor Golovchanskiya,b
, Vitaly V. Bolginova,c
, Nikolay N. Abramova
, Valery V.
Ryasanova,c
a
: National University of Science and Technology MISIS, Moscow, Russia
b
: Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia
c
: Institute of Solid State Physics, Russian Academy of Science, Chernogolovka, Moscow
Region, Russia
Report time: see page 5; Contact e-mail: ig684@uowmail.edu.au
Abstracts
26

A novel Josephson magnetic memory element based on Josephson supercon-
ductor/ferromagnet/superconductor tunnel junction (SFS junction) is presented.
Josephson barrier is a Pd0.99Fe0.01 ferromagnetic layer with in-plane magnetic
anisotropy and small coercive ield. An application of small external magnetic
ield changes the magnetization of ferromagnetic layer that in turn changes the
junction critical current , allowing the realization of two distinct states with high
and low corresponding to logical “0” and logical “1” states respectively [1-3].
Dynamical properties (i.e. gyromagnetic ratio, Gilbert damping constant, etc.) of
Pd0.99Fe0.01 ferromagnetic layer are investigated separately employing high sensi-
tive ferromagnetic resonance experiment. A re-magnetization (switching) process
of Pd0.99Fe0.01 layer is studied numerically and limiting magnetization switching
rate is derived.
References:
1. V.V. Bol’ginov, V.S. Stolyarov, D.S. Sobanin, A.L. Karpovich, and V.V.
Ryazanov, JETP Lett. 95, 366 (2012).
2. Valery V. Ryazanov, Vitaly V. Bol’ginov, Danila S. Sobanin, Igor V. Vernik,
Sergey K. Tolpygo, Alan M. Kadin, and Oleg A. Mukhanov, Physics Procedia
36, 35 (2012).
3. I.V. Vernik, V.V. Bol’ginov, S.V. Bakurskiy, A.A. Golubov, M.Yu. Kupriyanov,
V.V. Ryazanov, and O.A. Mukhanov, IEEE Trans. Appl. Supercond. 23,
1701208 (2013).
Spectroscopy of Surface Andreev Bound States in Topological
Insulator / Superconductor Junctions
Alexander Golubov1,2
, M. Snelder1
, Y. Asano2,3
, M Stehno1
, and A. Brinkman1
1
: Faculty of Science and Technology and MESA; Institute of Nanotechnology, University
of Twente, Netherlands
2
3
: Hokkaido University, Sapporo, Japan
Report time: see page 10; Contact e-mail: a.golubov@utwente.nl
The results of recent studies of superconducting junctions on surfaces of topo-
logical insulators are presented. To guide experimental work on the search for
Majorana zero-energy modes, we calculate the superconducting pairing symme-
try of a three-dimensional topological insulator in combination with an s-wave
superconductor. In analogy to the case of nanowires with strong spin-orbit cou-
pling we show how the pairing symmetry changes across diferent topological
regimes. We demonstrate that a dominant p-wave pairing relation is not sui-
cient to realize a Majorana zero-energy mode useful for quantum computation.
Abstracts
27

The relation between odd-frequency pairing and Majorana zero energy modes
is derived by using Green functions techniques in three-dimensional topological
insulators in the so-called Majorana regime. We discuss thereafter how the pair-
ing relations in the diferent regimes can be observed in the shape of the tunnel-
ing conductance of an s-wave proximized three-dimensional topological insula-
tor. We discuss the necessity to incorporate a ferromagnetic insulator to localize
the zero-energy bound state to the interface as a Majorana mode. We also present
the results of conductance spectroscopy measurements of a proximity induced
superconducting topological insulator. We study the proximity efect between
the fully-gapped region of a topological insulator in direct contact with an s-wave
superconducting electrode (STI) and the surrounding topological insulator lake
(TI) in Au/Bi1.5Sb0.5Te1.7Se1.3/Nb devices. The conductance spectra of the devices
show the presence of a large induced gap in the STI as well as the induction of su-
perconducting correlations in the normal part of the TI on the order of the Thou-
less energy. The shape of the conductance modulation around zero-energy varies
between devices and can be explained by existing theory of s-wave-induced su-
perconductivity in SNN’ (S is a superconductor, N a superconducting proximized
material and N’ is a normal metal) devices.
Anomalous Proximity Efect and More Than One Majorana
Fermion
Satoshi Ikegaya, Y. Asano
Department of Applied Physics, Hokkaido University, Sapporo 060-8628, Japan
Report time: see page 5; Contact e-mail: satoshi-ikegaya@eng.hokudai.ac.jp
Physics of Majorana fermion has been a hot issue in condensed matter
physics.฀Within this context, the anomalous proximity efect of spin-triplet su-
perconductors฀has been growing its importance because the efect is a direct re-
sult of the existence of Majorana fermion bound states.฀An isolating spin-triplet
� -wave superconductor, for instance, traps highly degenerated Majorana bound
states at its edges. When we attach the normal metal to the � -wave supercon-
ductor, the Majorana bound states penetrate into the normal metal and enhance
the local density of states at the zero energy [1]. The penetrated Majorana bound
states induce various anomalous electromagnetic properties in the normal metal.
For example, a perfect Andreev relection from a � -wave superconductor into a
dirty normal metal causes anomalous low energy transport in the -direction such
as a zero-bias conductance quantization in normal-metal/superconductor (NS)
junctions [2]. The perfect quantization of the zero-bias conductance in the disor-
Abstracts
28

dered junction is an aspect of the anomalous proximity efect. The zero-bias con-
ductance quantization implies that the penetrated Majorana fermions retain their
high degeneracy even in the impurity potentials and form the resonant transmis-
sion channels there. However, it has been unclear what symmetry protects the
degeneracy of Majorana fermions in the dirty normal metal and why the perfect
Andreev relection persists at zero-energy.
Recent theoretical studies have shown that chiral symmetry is responsible for
the stability of more than one Majorana fermion [3]. On the basis of the novel in-
sight, we successfully explain the stability of the degenerated Majorana fermions
in the disordered normal metal and prove the perfect Andreev relection irrespec-
tive of impurity potentials [4]. In our poster, we explain how chiral symmetry
protect the degeneracy and how chiral nature of � -wave superconductor induce
the perfect Andreev relection.
References:
1. Y. Tanaka, Y. Asano, A. A. Golubov, and S. Kashiwaya, Phys. Rev. B 72,
140503(R) (2005).
2. Y. Tanaka and S. Kashiwaya, Phys. Rev. B 70, 012507 (2004).
3. S. Tewari and J. D. Sau, Phys. Rev. Lett. 109, 150408 (2012).
4. S. Ikegaya, Y. Asano, and Y. Tanaka, Phys. Rev. B 91, 174511(2015).
High- and Low Superconductivity and Superluidity in
Fermi-Systems with Repulsion
Maxim Kagan
P.L. Kapitza Institute for Physical Problems, RAS, Moscow
Report time: see page 7; Contact e-mail: kagan@kapitza.ras.ru
Recent discovery of Cooper pairing at 190 K in metallic hydrogen sulide un-
der pressure revives the hopes to proceed from high- to room superconduc-
tivity. In the same time there are many interesting low- superconductive and
superluid systems.
In the present talk we discuss high- and low superconductivity and su-
perluidity in 3D and 2D fermionic systems with purely repulsive interaction. We
construct the phase-diagrams and ind the regions of superconductive pairings in
free space and on diferent lattices in Hubbard, t-J and other models of strongly
correlated electron systems. We demonstrate the possibility to increase signii-
cantly already at low density of fermions in the spin-polarized case and in the two-
band situation. The proposed theory can explain or predict superconductivity in
diferent materials including high- superconductors, low heterostructures
Abstracts
29

and semimetals, heavy fermions and organic superconductors. It explains angu-
lar dependence of the superconductive gap in FeAs-based superconductors and
predictis Kohn-Luttinger superconductivity in idealized monolayer and bilayer
graphene. For physics of quantum liquids and gases the theory predicts triplet
p-wave superluidity in 3D and 2D mixtures of He-3 in He-4 and in ultracold
Fermi-gases in magnetic traps, as well as a strong increase in spin-polarised
A1-phase of the superluid He-3. The potential for the experimental realization of
“high- ” superluidity in spin-polarized (imbalanced) Fermi-gases has the group
of J.E.Thomas in North Carolina. The physics of Dirac points in graphene has im-
portant analogies with the 2D honeycomb optical lattices studied by T.Esslinger
team in Zurich.
Dielectric Susceptibility of Magnetoelectric Thin Films with
Vortex-Antivortex Dipole Pairs
Petr Karpov, Sergei Mukhin
Department of Theoretical Physics and Quantum Technologies, National University of
Science and Technology MISiS, Leninski avenue 4, 119049, Moscow, Russia
Report time: see page 5; Contact e-mail: karpov.petr@gmail.com
In the present work [1] we consider a model for magnetoelectric or type-II mul-
tiferroic [2] thin ilms and ind the inluence of metastable micromagnetic struc-
tures (vortex-antivortex pairs) on electric properties (dielectric susceptibility) of
the system.
We describe the magnetic subsystem using continuous version of the 2D XY
model (XY plane coincides with the ilm plane). It is well known [3,4] that in
such systems vortices play an important role: below � (Berezinskii-Kosterlitz-
Thouless temperature) vortices and antivortices are bound in pairs and when the
temperature rises above � the pairs dissociate.
If we now include the interaction between the electric and magnetic subsys-
tems in form of [5]
� −��((�∇)� − �(∇�))
( is the interaction energy density, � is the polarization, � is the magnetiza-
tion, � is the coupling constant), then magnetic vortices acquire electric charges.
In the work we calculate the contribution of the vortex dipole pairs to the dielectric
susceptibility of the system at � � .
In order to do this, we write the grand partition function for the vortex-
antivortex dipole gas in the external electric ield. It turns out that it is possible
to calculate the grand partition function in the approximation of noninteracting
Abstracts
30

dipole pairs and to obtain the contribution of the pairs to the electric susceptibil-
ity �
( )
(which is the main result of the paper). As → � the susceptibility takes
an activation exponential form �
( )
( ) ∼ exp(−� � ) (� is the vortex-antivortex
creation energy) and as → � it diverges as �
( )
( ) ∼ | − � |− . However,
we expect that in the vicinity of � the interaction of dipole pairs becomes im-
portant and, therefore, at � susceptibility stays inite. Nevertheless one should
observe a sharp peak in �
( )
( ) dependence at ≈ � in the experimental data.
References:
1. P.I. Karpov, S.I. Mukhin. Dielectric susceptibility of magnetoelectric thin ilms with
vortex-antivortex dipole pairs. arXiv:1506.07856 (2015).
2. D.I. Khomskii. Classifying multiferroics: Mechanisms and efects. Physics 2, 20
(2009).
3. J.M. Kosterlitz and D.J. Thouless. Ordering, metastability and phase transitions
in two-dimensional systems. J.Phys. C6, 1181 (1973).
4. V.L. Berezinskii. Destruction of long-range order in one-dimensional and two-
dimensional systems having a continuous symmetry group I. Classical systems.
Sov.Phys. JETP 32, 493 (1971).
5. M.V. Mostovoy. Ferroelectricity in spiral magnets. Phys.Rev.Lett. 96, 067601
(2006).
Current Transport in SF-NFS Josephson Structures: Theory and
Application
I. I. Soloviev1,2
, Nikolay Klenov3,2
, S. V. Bakurskiy3,4,5
, V. V. Bol’ginov6,7
, V. V.
Ryazanov6,7
, M. Yu. Kupriyanov1,4
, and A. A. Golubov4,5
1
: SINP, MSU, Moscow, Russia
2
: NIIFP, Zelenograd, Russia
3
: Physics Department, MSU, Russia
4
: MIPT, Dolgoprudniy, Russia
5
: University of Twente, The Netherlands
6
: ISSP, Chernogolovka, Russia
7
: NUST MISiS, Moscow, Russia
Report time: see page 9; Contact e-mail: nvklenov@gmail.com
We propose a control element for a Josephson spin valve. It is a complex
Josephson device containing ferromagnetic (F) layer in the weak-link area consist-
ing of two regions, representing 0 and p Josephson junctions, respectively. The
valve’s state is deined by mutual orientations of the F-layer magnetization vector
and boundary line between 0 and p sections of the device. We consider possi-
ble implementation of the control element by introduction of a thin normal metal
Abstracts
31

layer in a part of the device area. By means of theoretical simulations, we study
properties of the valve’s structure as well as its operation, revealing such advan-
tages as simplicity of control, high characteristic frequency, and good legibility of
the basic states.
In addition we discuss several general properties of the current transport
through a long Josephson junction with alternating critical current density. This
alternating density can be achieved in experiment by incorporating of the mag-
netic layer to the weak link in a special way. Prospects for the practical use of such
structures are related to the possibility of obtaining bistable Josephson elements
on their basis. Joint analysis for both the current-phase relations and the dynamic
characteristics allowed to optimize the operation mode for fast superconducting
memory cell based on the bistable contact and to assess the energy dissipation for
”Read” and ”Write” operations.
Controllable Tuning of Spin-Singlet and Spin-Triplet Currents in a
Josephson Spin-Valve
A. Iovan, T. Golod, and Vladimir Krasnov
Stockholm University, AlbaNova University Center, SE-10691 Stockholm, Sweden
Report time: see page 4; Contact e-mail: vladimir.krasnov@fysik.su.se
It has been predicted theoretically [1,2] that the proximity efect in a supercon-
ducting spin-valve should strongly depend on a relative orientation of magnetiza-
tion in ferromagnetic layers of the spin valve. An exotic spin-triplet component of
the superconducting order parameter can be generated in the non-collinear state
of the superconducting spin-valve. Several experimental reports, conirming such
a behavior, has been made [3-5]. However, unambiguous interpretation of the
data requires accurate control of the spin-valve state. This also presumes a mono-
domain state of the spin-valve, which requires special care.
In this talk we present our recent results on experimental analysis of nano-
scale superconducting spin-valve devices, in which a spin valve structure is imple-
mented as a barrier in a Josephson junction. Nano-scale junctions with sizes down
to 150 nm were patterned by photolithography, reactive ion etching and three-
dimensional nano-sculpturing using focused ion beam, as described in Ref. [6].
Small dimensions were necessary both for mono-domain switching of spin valves
and for enhancement of junction resistances to comfortably measurable values.
Ferromagnetic layers in the spin-valve are made dissimilar using a combination of
diluted (CuNi) ferromagnets with diferent Ni concentration of with combination
of diferent strong (Ni, Co, Py) ferromagnets. Our Josephson spin-valves exhibit
Abstracts
32

both clear Fraunhofer-type modulation of the Josephson critical current ( ), in-
dicating good homogeneity of the Josephson current through the spin valve, and
a regular spin-valve magnetoresistance with minima at the parallel and maxima
at the anti-parallel orientation of magnetization of the two ferromagnetic layers
[7].
We put special eforts to development of accurate ways for in-situ analysis of
the spin-valve state. We demonstrate how two-dimensional angular orientation
of magnetic moments of ferromagnetic layers in the spin-valve can be accurately
measured in-situ. This allows us to make an unambiguous connection between
the relative orientation of magnetizations and the amplitude of the Josephson cur-
rent, which indicate that both the spin-singlet and the spin-triplet components of
the supercurrent are tuned with changing the orientation of the spin-valve.
References:
1. A. I. Buzdin, Rev. Mod. Phys. 77, 935 (2005).
2. F. S. Bergeret, A. F. Volkov, and K. B. Efetov, Rev. Mod. Phys. 1321 (2005).
3. C. Bell, G. Burnell, C. W. Leung, E. J. Tarte, D.-J. Kang, and M. G. Blamire,
Appl. Phys. Lett. 84, 1153 (2004).
4. T. S.Khaire, M. A. Khasawneh, W. P. Pratt, Jr., and N. O. Birge, Phys. Rev.
Lett. 104, 137002 (2010).
5. P. V. Leksin, N. N. Garif’yanov, I. A. Garifullin, J. Schumann, V. Kataev, O.
G. Schmidt, and B. Buchner, Phys. Rev. Lett. 106, 067005 (2011).
6. T. Golod, A. Rydh, and V.M. Krasnov, Phys. Rev. Lett., 104, 227003 (2010).
7. A. Iovan, T. Golod, and V.M. Krasnov, Phys. Rev. B, 90, 134514 (2014).
Josephson Efect in SIFS Tunnel Junctions with Complex
Barriers in Weak Link Region
S.V. Bakurskiy+∗
, A.A.Baranov∗
, A.A.Golubov∗×
, N.V.Klenov+
, Mikhail
Kupriyanov∗◦฀
, I. I. Soloviev◦
+
: Physics Department, Lomonosov MSU, 119991 Moscow, Russia
∗
: Moscow Institute of Physics and Technology, 141700 Dolgoprudniy, Russia
×
: Faculty of Science and Technology and MESA+, Institute for Nanotechnology,
University of Twente, 7522 NB Enschede, Netherlands
◦
: Skobeltsyn Institute of Nuclear Physics, Lomonosov MSU, 119991 Moscow, Russia
฀
: Institute of Physics, Kazan (Volga region) Federal University, 420008 Kazan, Russia
Report time: see page 12; Contact e-mail: mkupr@pn.sinp.msu.ru
We study theoretically the properties of SIFS type Josephson junctions com-
posed of two superconducting (S) electrodes separated by an insulating layer (I)
and a ferromagnetic (F) region consisting of periodic magnetic domains structure
Abstracts
33

with antiparallel magnetization directions in neighboring domains. Two domain
alignments have been considered. In the irst geometry it is supposed that the
domain structure is formed in a single ferromagnetic ilm. It is a periodical struc-
ture in the direction perpendicular to the current lowing through the junction.
In the second geometry it is considered that the Josephson coupling occurs in
SFNFN…FNIS structures, in which in weak link there is a FNFN…FN multilayer
with FN interfaces located perpendicular to the direction of supercurrent low.
For the irst geometry the two-dimensional problem in the weak link area is
solved analytically in the framework of the linearized quasiclassical Usadel equa-
tions. Based on this solution, the spatial distributions of the critical current den-
sity, Jc, in the domains and critical current, Ic of SIFS structures are calculated as
a function of domain wall parameters, as well as the thickness, dF and the width,
W, of the domains. We demonstrate that Ic(dF,W) dependencies exhibit damped
oscillations with the ratio of the decay length, xi1, and oscillation period, xi2, be-
ing a function of the parameters of the domains, and this ratio may take any value
from zero to unity. Thus, we propose a new physical mechanism that may explain
the essential diference between xi1 and xi2 observed experimentally in various
types of SFS Josephson junctions.
In the second geometry we study the proximity efect in SFNFN…FN elec-
trode in the frame of Usadel equations both analytically (in the linear approxi-
mation) and numerically. We have shown that depending on the layers thickness
and magnitude of suppression parameters gamma and gammaB superconducting
correlations can monotonically decay in FNFN..FN multilayer or exhibit damped
oscillations and calculate the decay length, xi1, and oscillation period, xi2, as a
function of layers thickness and suppression parameters at FN boundaries.
This work was supported by RFBR grants l4-02-90018-bel a, 14-02-31002-mol
a, 15-32-20362-mol a ved, Ministry of Education and Science of the Russian Fed-
eration in the framework of Grant No. 14Y26.31.0007 and the Program for the
Promotion of Competitiveness of the Kazan Federal University among the World-
Leading Scientiic Educational Centers, Russian President grant MK-1841.2014.2,
Dynasty Foundation, Scholarship of the President of the Russian Federation and
Dutch FOM.
SnS-Andreev Spectroscopy of Fe-based Oxypnictides: Scaling of
Superconducting Parameters with �
Tatiana Kuzmicheva1,2
, S.A. Kuzmichev2
, Ya.G. Ponomarev2
, V.M. Pudalov1
1
: P.N. Lebedev Physical Institute, Russian Academy of Sciences, 119991 Moscow, Russia
Abstracts
34

2
: M.V. Lomonosov Moscow State University, 119991 Moscow, Russia
Report time: see page 3; Contact e-mail: kute@sci.lebedev.ru
We studied high-temperature oxypnictide (so called 1111 family) Fe-based
superconductors LaO1–xFxFeAs, GdO1–xF฀FeAs, GdO1–δFeAs, Sm1–xThxOFeAs
and CeO1–xFxFeAs with the � range �� − �� K by Andreev and intrinsic An-
dreev spectroscopies [1,2]. Intrinsic multiple Andreev relections efect was irstly
observed in 1111-oxypnictides, revealing the Andreev-like transport along the c-
direction. We determined the values of two bulk superconducting gaps and their
BCS-ratios, and demonstrated weak anisotropy of Δ (�� − ��%) and the absence
of nodes in Δ . For the maximal � ≈ �� K, we found Δ � �� ± �� meV,
Δ � �� ± �� meV, Δ �Δ ≈ ��.
The gap temperature dependences Δ � ( ) agree well with two-band model
by Moskalenko and Suhl [3]. Both gaps turn to zero at common critical tempera-
ture. Using itting of the experimental Δ � ( ) by the two-band model, we deter-
mined some parameters of superconducting state of 1111-materials directly from
the experiment.
The estimated relative coupling constants � were shown to be
� �� |� |�|� | ≈ �� within the range � � �� − �� K. We
demonstrate scaling of both superconducting gaps with � (Fig. 1) and nearly
constant BCS-ratio �Δ � � � ≈ ��. For each condensate, the eigen BCS-ratio
was estimated (in a hypothetical case of zero interband coupling, � , � � �):
for the large gap we get �Δ � � � ≈ ��, for the small gap �Δ � � � ≈ ��,
�� ≈ ��8. These values exceed the weak-coupling limit but are in frames of
Eliashberg theory thus pointing to a strong electron-phonon intraband coupling
in two condensates. The lanthanide-� spacers were shown to act as charge
reservoirs.
Abstracts
35

Fig 1: The dependence of the large superconducting gap (solid symbols) and
the small gap (open symbols) on the critical temperature for oxypnictides and
FeSe. The weak-coupling BCS-limit is shown by dash-dot line for comparison.
References:
1. T.E. Kuzmicheva, et al., EPL 102, 67006 (2013)
2. T.E. Kuzmicheva, et al., Physics-Uspekhi 57, 819 (2014)
3. V.A. Moskalenko, Fiz. Met. Metall. 8, 503 (1959); H. Suhl, et al., Phys. Rev.
Lett. 3, 552 (1959)
Paramagnon Excitations Theory for Magnetic Properties of
Layered Copper Oxide Superconductors
Igor Larionov
National University of Science & Technology ”MISIS”, 119049, Moscow, Russia
Kazan Federal University, 420008, Kremlevskaya, 18, Kazan, Russia
Report time: see page 3; Contact e-mail: Larionov.MRSLab@mail.ru
Using a relaxation function theory we obtain and analyze the dynamic spin
susceptibility expressions for doped � �� two-dimensional Heisenberg antifer-
romagnetic (AF) model in the paramagnetic phase taking into account the thermal
damping efects of spin wave-like (paramagnon-like) excitations. The relaxation
Abstracts
36

function theory is widely applicable for describing the properties of nonequilib-
rium systems and by itself the Markovian situation can be valid even in the ab-
sence of any picture of the system in terms of well-deined excitations [1]. The
presentation is valid for all wave vectors throughout the Brillouin zone.
The role of damping (lifetime) of paramagnon excitations, its evolution with
doping and temperature, is highlighted in view of magnetic response of high-
layered cuprates. It is shown [2] that the theory is able to explain the main
experimentally observed features in the imaginary part of the dynamic spin sus-
ceptibility in La2–xSrxCuO4 and YBa2Cu3O7–δ as obtained by resonant inelastic
X-ray scattering (RIXS) [3]. The calculated dynamic spin susceptibility [4] gives
also a reasonable agreement with neutron scattering experiments [5] and nuclear
spin-lattice relaxation rates �� [6] data from pure AF insulator right up to opti-
mally doped high- ’s in the normal phase. It is shown that RIXS data analysis
depends on paramagnon damping and thus afected by approximations made for
expressions for dynamic spin susceptibility.
References:
1. U. Balucani, M. H. Lee, and V. Tognetti, Phys. Rep. 373, 409 (2003).
2. I.A. Larionov, Solid State Commun. 208, 29 (2015) and to be published.
3. M. Le Tacon, G. Ghiringhelli, J. Chaloupka, M. Moretti Sala, V. Hinkov, M.
W. Haverkort, M. Minola, M. Bakr, K. J. Zhou, S. Blanco-Canosa, C. Monney,
Y. T. Song, G. L. Sun, C. T. Lin, G. M. De Luca, M. Salluzzo, G. Khaliullin, T.
Schmitt, L. Braicovich, B. Keimer, Nature Physics Vol. 7, 725-731 (2011).
4. I.A. Larionov, Phys. Rev. B 69, 214525 (2004); 72, 094505 (2005); 76, 224503
(2007)
5. B. Keimer, N. Belk, R. J. Birgeneau, A. Cassanho, C. Y. Chen, M. Greven, M.
A. Kastner, A. Aharony, Y. Endoh, R. W. Erwin, and G. Shirane, Phys. Rev.
B 46, 14034 (1992).
6. T. Imai, C. P. Slichter, K. Yoshimura, and K. Kosuge, Phys. Rev. Lett. 70,
1002 (1993).
Josephson Junction Detectors for Majorana and Dirac Fermions
Moitri Maiti1
, K. M. Kulikov1
, K. Sengupta2
, and Y. M. Shukrinov1
1
: BLTP, JINR, Dubna, Russia
2
: Indian Association for the Cultivation of Science, Kolkata, India
Report time: see page 10; Contact e-mail: maiti@theor.jinr.ru
We demonstrate that the current—voltage (I—V) characteristics of resistively
and capacitiver shunted Josephson junctions (RCSJ) of topological superconduc-
tors hosting localized subgap Majorana states provides a phase sensitive method
Abstracts
37

for their detection. We show that the I—V characteristics of such RC—SJ s display
a novel devil staircase structure for Shapiro steps which is qualitatively difer-
ent from those found in conventional superconductors. A similar study for RCSJ
with graphene superconducting junctions hosting Dirac—like quasiparticles re-
veals that the Shapiro step width in their I—V curves oscillates with the junction
barrier potential. We demonstrate that this oscillatory feature is a signature of the
underlying Dirac quasiparticles.
Three Component Spin-Charge Superconducting Order
Parameter and Pair Density Waves in Correlated Fermi Systems
in a Magnetic Field
Sergei Matveenko
Landau Institute for Theoretical Physics, Moscow
Report time: see page 2; Contact e-mail: matveen@itp.ac.ru
A irst-order phase transition is predicted between a spatially homogeneous
superconducting state and a state with a space-modulated composite spin-charge-
superconducting order parameter in an applied external magnetic ield. In this
state the superconducting order changes sign when entering the “stripe-phase”
ordered domain. Corresponding self-consistent solutions of the Bogoliubov-de
Gennes equations are found in an analytic form for the two-dimensional Hubbard
t-U-V model with �− � symmetry of the superconducting order parameter in an
external magnetic ield.
Microscopic Theory of Vortex Pinning on Columnar Defects in
Conventional, Chiral and Ferromagnetic Superconductors
Alexander Mel’nikov1,2
, A.V.Samokhvalov1
, and V.Vadimov1,2
1
: Institute for Physics of Microstructures, RAS, Nizhny Novgorod, Russia
2
: Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia
Report time: see page 8; Contact e-mail: melnikov@ipmras.ru
The electronic structure of a vortices pinned by an insulating columnar in-
clusions in type-II superconductors is studied within the Bogolubov-de Gennes
theory. For conventional s-wave superconductors we ind the modiication of the
anomalous spectral branch in the quasiparticle spectrum caused by the electron
scattering at the defect. For a chiral px+i py superconductor the structure of the
Abstracts
38

anomalous spectral branch is shown to be strongly afected by the mutual orienta-
tions of the angular momenta of the center of mass and the relative motion of the
two electrons in the Cooper pair. Being only slightly perturbed by the scattering
at the defect for the zero sum of these angular momenta the anomalous spectral
branch appears to change dramatically in the absence of such compensation. In
the latter case the defect presence changes the anomalous branch slope sign at
the Fermi level resulting in the quasiparticle angular momenta inversion at the
positive energies and the impact parameters smaller than the defect radius. We
analyze also the pinning and electronic structure of multiquanta vortices.
The experimentally observable consequences for the scanning tunneling mi-
croscopy characteristics and high-frequency ield response (in particular, Kerr ef-
fect) are discussed. The individual pinning potentials and corresponding depin-
ning currents are evaluated. The chiral superconductors are shown to reveal a
strong dependence of the pinning characteristics on the mutual orientation of the
magnetic ield and internal angular momentum of the Cooper pair. The pinning
phenomena in chiral are also shown to be strongly afected by the quasiparticle
edge currents lowing around the insulating defects. The resulting contribution
to the pinning potential is found to be similar to the one for pinned vortices in
ferromagnetic superconductors.
Triplet Proximity Efect in Superconducting Heterostructures with
a Half-Metallic Layer
Sergey Mironov1,2,3
and A. Buzdin1
1
: University Bordeaux, Talence Cedex, France
2
3
: Institute for Physics of Microstructures RAS, Nizhny Novgorod, Russia
Report time: see page 9; Contact e-mail: sermironov@rambler.ru
We present the Usadel theory describing the superconducting proximity ef-
fect in heterostructures with a half-metallic layer. It is shown that the full spin po-
larization inside the half-metals gives rise to the giant triplet spin-valve efect in
superconductor (S) – ferromagnet (F) – half-metal (HM) trilayers as well as to the
phi-junction formation in the S/F/HM/F/S systems. In addition, we consider the
exactly solvable model of the S/F/HM trilayers of atomic thickness and demon-
strate that it reproduces the main features of the spin-valve efect found within the
Usadel approach. Our results are shown to be in a qualitative agreement with the
recent experimental data on the spin-valve efect in MoGe/Cu/Ni/CrO2 hybrids
[A. Singh et al., arXiv:1410.4973].
Abstracts
39

Interference of Triplet -wave Condensates in Coupled
Josephson Junctions
Andreas Moor1
, A.F. Volkov1
, K.B. Efetov1,2
1
: Ruhr-Universität Bochum, Germany
2
: NUST “MISiS”, Moscow, Russia
Report time: see page 9; Contact e-mail: amoor@tp3.rub.de
Interest in studying triplet superconducting correlations in superconduc-
tor/ferromagnet (S/F) hybrids has substantially increased during the past decade
(see reviews and references therein [1,2]). In this talk we present results of the
theoretical study of dc Josephson efect in a multiterminal structure of cross-type
geometry in which the Josephson coupling between is realized through the long-
range triplet component (LRTC). The triplet Cooper pairs are created in S/F
(S �S/F ) bilayers with a good interface which consist of a standard singlet BCS
superconductors S and a weak ferromagnet with an exchange ield �. The singlet
component is separated by spin ilters Fl (magnetic insulator) or by a strong fer-
romagnet F . We show that the LRTCs interfere if the magnetic moments in spin
ilters are oriented in the same direction. If the vectors � are parallel, the Joseph-
son current in the considered system S /Fl - n - S /Fl has the standard phase
dependence � − sin �, but the critical current is negative (�-junction), where
n is a normal wire. In case of perpendicular �, the current is not zero at � � �
(� - contact). In other words a spontaneous current may appear in the system.
Interestingly, although the ilters, for example, pass only electrons with spin up,
in the n-wire exist triplet Cooper pairs with both spin up and down. The results
for a system in which the ilters are replaced by a strong ferromagnet difer from
those obtained for the system with ilters.
References:
1. F. S. Bergeret, A. F. Volkov, K. B. Efetov, Rev. Mod. Phys. 77, 1321 (2005).
2. M. Eschrig, Physics Today, 64, 43 (2011).
Geometrically Controlled Quantum Coherence and
Non-Equilibrium Efects in Nanoscopic Kondo Droplets
Dirk Morr
University of Illinois at Chicago, USA
Report time: see page 7; Contact e-mail: dkmorr@uic.edu
Abstracts
40

The nature of strong correlations and quantum coherence in macroscopic
Kondo lattices, as realized in heavy fermion materials, still eludes theoretical un-
derstanding. Atomic manipulation to assemble nanoscopic lattices of magnetic
atoms on metals – Kondo droplets – provides a new approach to study and con-
trol the emergence of quantum coherence and interaction efects at the nanoscale,
and thus bridge the gap between the single Kondo impurity and the ininite lat-
tice. In this talk, I review some recent progress in controlling quantum coherence
and interactions in atomically precise periodic arrangements of magnetic atoms
on metallic surfaces using scanning tunneling microscopy (STM). I show how
quantum-coherent coupling between individual Kondo resonances can be geo-
metrically controlled, leading to local Kondo temperatures that are signiicantly
enhanced over that of a single magnetic atom. Moreover, I demonstrate how the
non-equilibrium transport properties of Kondo droplets provide new insight into
the nature of strong correlations.
Fluctuations of “Hidden Order” as Cooper Pairing Glue
Sergei Mukhin
Moscow Institute for Steel and Alloys, Moscow, Russia
Report time: see page 7; Contact e-mail: i.m.sergei.m@gmail.com
Fluctuations of the “hidden order” as an origin of the Cooper pairing glue
in high- superconductors is discussed. New scenario is based on the recent
publications [1]-[3] that introduced Euclidean crystallization in correlated fermi-
system as an origin of a “hidden order”, that breaks translational invariance of
the system along the Matsubara time exis. Spin-density wave with Matsubara
time-periodic amplitude is considered as a particular case of the “hidden order”.
Fluctuations of this peculiar order parameter are found self-consistently and their
role in providing a Cooper pairing glue in the fermi-system is investigated. The
work advances the previuos results. Namely, it was proven analytically [1] that
self-consistent Matsubara time-periodoc order parameter, built of Jacobian ellip-
tic function, has zero scattering cross section and, therefore, is a candidate for a
“hidden order”, emerging in the fermi-systems like high- cuprates. Simulta-
neously, it is proven now analytically that this order parameter itself is only a
metastable state of the fermi-system. The discrete spectrum of the “hidden or-
der” luctuations is found using Lame functions theory. The new result consists
in the derivation, that shows how luctuations of the “hidden order”, forming a
discrete spectrum [2], [3], renormalize under the Cooper pairing in fermionic sys-
tem. The self-consistent solution minimizing the efective Euclidean action of the
fermi-system in a form of Landau-Ginzburg-Wilson functional with two coupled
Abstracts
41

orders is found analytically as the major outcome of the work. Possible relation of
the theory to the physics of high- cuprates is discussed.
References:
1. S. I. Mukhin, «Spontaneously broken Matsubara’s time invariance in
fermionic system: macroscopic quantum ordered state of matter», J. Super-
cond. Nov. Magn., vol. 24, 1165-1171 (2011).
2. S. I. Mukhin , «Euclidean action of fermi-system with ”hidden order”, Phys-
ica B: Physics of Condensed Matter,v. 460, 264 (2015).
3. S. I. Mukhin, «Euclidian Crystals in Many-Body Systems: Breakdown of
Goldstone’s Theorem», J. Supercond. Nov. Magn.,vol.27, 945-950 (2014).
Charge Imbalance in a Stack of Intrinsic Josephson Junctions
Under External Radiation
Yury Shukrinov1,2
, Majed Nashaat3
, Kulikov Kulikov1,2
, Radwa Dawood3
,
Hussein El Samman4
and Th. M. El Sherbini3
1
: BLTP, Joint Institute for Nuclear Research, Dubna, Russia
2
: Dubna International University of Nature, Society, and Man, Dubna, Russia
3
: Department of Physics, Faculty of Science, Cairo University, Egypt
4
: Department of Physics, Faculty of Science, Menouiya University, Egypt
Report time: see page 3; Contact e-mail: majed@sci.cu.edu.eg
The nonequilibrium efects play an important role in a stack of intrinsic Joseph-
son junctions (IJJs) in high temperature superconductors because the thickness of
the superconducting layers is very small. Such efects can be manifested in a shift
of the condensate chemical potential and charge imbalance efect, where an elec-
tron and a hole like quasi-particle distributions are diferent.
We investigate the efects of the non-stationary nonequilibrium charge imbal-
ance on the phase dynamics for a stack of IJJs with diferent boundary condi-
tions. The current-voltage characteristics of capacitively coupled Josephson junc-
tions with the charge imbalance are numerically calculated and a precise numer-
ical study is performed for a stack of IJJs under radiation. The efect of charge
imbalance is observed on the Shapiro step that shows a inite slope depending on
the nonequilibrium parameter, which is a function of the quasi-particle relaxation
time and the thickness of the superconducting layer. We demonstrate the shift of
the Shapiro step from its canonical position determined by the frequency of the
external radiation.
Abstracts
42

FSF Spin-Valves: Comparison of Diferent Models
Nataliya Pugach1
, M. Eschrig2
, M. G. Flokstra3
, T. C. Cunningham3
, J. Kim4
, N.
Satchell4
, G. Burnell4
, P. J. Curran5
, S. J. Bending5
, C. Kinane6
, A. Isidori2
, J. F. K.
Cooper6
, S. J. Langridge6
, S.L. Lee3
1
: Skobeltsyn Institute of Nuclear Physics, MSU, Moscow.
2
: University of London Egham, Surrey, TW20 0EX, UK.
3
: School of Physics and Astronomy, SUPA, University of St.Andrews, KY16 9SS, UK.
4
: School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK.
5
: University of Bath, Claverton Down, Bath, BA2 7AY, UK.
6
: ISIS, Rutherford Appleton Laboratory, Oxfordshire OX11 0QX, UK.
Report time: see page 4; Contact e-mail: pugach@magn.ru
In 1999 the superconducting spin-valve was proposed theoretically [1,2], com-
prising a superconducting (S) spacer layer separating two ferromagnetic (F) layers.
For ideal operation, the in-plane supercurrent in the S layer can be controlled by
the mutual orientation of magnetization in the F layers. Initially the spin-valve
efect was observed as a dependence of the critical temperature ( ) on the mag-
netic coniguration, parallel (P) or antiparallel (AP) in such structures. However,
the change between collinear and perpendicular coniguration may be much
more pronounced than between P and AP alignment in a case of a strongly spin-
polarized ferromagnet [3-5] due to appearance of the new channel for drainage
of Cooper pairs from the S to the F layers related to appearance of the long-range
triplet superconducting correlations (LRTC) [6,7].
We have calculated and observed [5] the angular dependence of the for FSF
as well as SFF Co-Nb spin-valves. For both sample types (SFF and FSF) a large sup-
pression of is found when the magnetizations are orthogonal, consistent with
the theoretical expectations for the drainage of singlet into the triplet LRTC chan-
nel when the magnetization is non-collinear. This magnetization alignment may
be controlled by an external magnetic ield. The efect almost disappears when
switching the spin-valve into a collinear state, when LRTC are absent. This shows
that LRTC in the ferromagnetic regions are a crucial ingredient contributing to the
efect.
We have developed and compared diferent models for the description of the
proximity efect between a usual superconductor and a strong ferromagnet. Such
spin-valves may serve as building blocks of spintronic devices and our investiga-
tion provide a mechanism by which such devices might be realized.
We acknowledge the support of the EPSRC through Grants No. EP/J01060X,
No. EP/J010626/1, No. EP/J010650/1, No. EP/J010634/1, and No.
EP/J010618/1, support of a studentship supported by JEOL Europe and the ISIS
Abstracts
43

Neutron and Muon Source, and the support of the RFBR via Awards No. 13-02-
01452-a, and No. 14-02-90018 BEL-a.
References:
1. A. I. Buzdin, A. V. Vedyayev and N. V. Ryzhanova, Europhys. Lett., 48 686-
691 (1999).
2. L. R. Tagirov, Phys. Rev. Lett. 83 2058 (1999).
3. P. V. Leksin, N. N. Garif’yanov, I. A. Garifullin, et al., Phys. Rev. Lett. 109
057005 (2012).
4. A. Singh, S. Voltan, K. Lahabi, J. Aarts. arXiv:1410.4973 (2014).
5. M. G. Flokstra, T. C. Cunningham, J. Kim, N. Satchell, G. Burnell, P. J. Cur-
ran, S. J. Bending, C. J. Kinane, J. F. K. Cooper, S. Langridge, A. Isidori, N.
Pugach, M. Eschrig, S. L. Lee. Phys. Rev. B 91, 060501(R) (2015).
6. Ya. V. Fominov, A. A. Golubov, and M. Yu. Kupriyanov, JETP Letters 77 510
(2003).
7. S. Mironov, A.I. Buzdin, Phys. Rev. B 89, 144505 (2014).
Peculiarities of DC-SQUIDs with Topologically Nontrivial Barrier
Ilhom Rahmonov � , Yu. M. Shukrinov � , K. Sengupta , R. Dawood �
: Umarov Physical and Technical Institute, Dushanbe, Tajikistan
: Dubna International University for Nature, Society and Man, Dubna, Russia
: Indian Association for the Cultivation of Science, Kolkata, India
: Cairo University, Giza, Egypt
Report time: see page 10; Contact e-mail: rahmonov@theor.jinr.ru
Josephson junctions with topologically nontrivial barriers host Majorana
bound states [1,2] Candidates with high potential for the detection and manipu-
lation of the Majorana fermion [3] are superconducting quantum interference de-
vices (SQUIDs) [4,5]. The appearance of Majorana bound states in superconduct-
ing junctions enables tunneling of quasiparticles with charge across the junction,
which doubles the Josephson periodicity � sin(��) [1].
We study in detail the behavior of DC-SQUIDs with topologically nontrivial
barriers and compare the results with the trivial case. The current voltage char-
acteristics and the critical current dependence on the external magnetic lux for
the dc SQUID with trivial and nontrivial barriers are presented. We have shown
that so-called beating solutions at the resonance frequency [6] of DC-SQUID with
nontrivial barriers shifts on √� in comparison with the case of trivial barriers. We
consider that this fact might be used in the experimental detecting of Majorana
fermions.
Abstracts
44

References:
1. L.Fu and C.L. Kane, Phys.Rev.Lett. 100, 096407 (2008).
2. Y.Tanaka, T. Yokoyama, and N. Nagaosa, Phys.Rev.Lett. 103, 107002 (2009).
3. E. Majorana, Nuovo Cimento 14, 171 (1937).
4. L. Fu and C. L. Kane, Phys.Rev.B 79, 161408 (R) (2009).
5. M. Veldhorst, C. G. Molenaar, C. J. M. Verwijs, H. Hilgenkamp, and A.
Brinkman, Phys.Rev.B 86, 024509 (2012).
6. W. -D. Schmidt, P. Seidel, and S. Heinemann, Phys.Stat.Sol.(a) 91, K155
(1985)
Peculiarity of Resonance Between Fluxon and Plasma Wave in
One-Dimensional Parallel Array of Josephson Junctions
Kirill Rodin1
, Ilhom Rahmonov2,3
, Yury Shukrinov1,2
1
: Dubna International University of Nature, Society, and Man, Dubna, Russia
2
3
: Umarov Physical and Technical Institute, Dushanbe, Tajikistan
Report time: see page 6; Contact e-mail: rayquaza@list.ru
We present results of the numerical studies of the propagation of Josephson
luxon and electromagnetic waves in parallel arrays of Josephson junctions [1]. A
series of resonances related to the locking between luxon rotation frequency and
the frequency of the radiated electromagnetic waves are observed in current volt-
age characteristics of the arrays [2]. Peculiarity of the resonance between luxon
and plasma wave and additional branch are found. The current voltage charac-
teristics manifest the hysteretic behavior near the peculiarity. We investigate the
voltage-time dependence at diferent values of bias current and make a detailed
FFT analysis of this dependence in current interval around the peculiarity. We
compare our results with data presented in Refs. [1,2].
Abstracts
45

Fig. 1
References:
1. A. V. Ustinov, M. Cirillo, B. A. Malomed. Phys. Rev.B, 47, 8357 (1993).
2. J. Pfeifer, A. A. Abdumalikov, Jr. M. Schuster, and A. V. Ustinov; Phys. Rev.
B, 77, 024511 (2008).
Quasi-Fermi Liquid: a Special State of One-Dimensional Matter
Alexander Rozhkov
ITAE RAN, Moscow, Russia; MIPT, Dolgoprudnyi, Russia
Report time: see page 2; Contact e-mail: arozhkov@gmail.com
It is well-known that the one-dimensional interacting fermions with marginal
(in the renormalization group sense) interaction cannot be described in terms of
the Fermi liquid. Instead, they present the phenomenology of the Tomonaga-
Luttinger liquid. Imagine that for some one-dimensional fermionic systems the
marginal part of the interaction is nulliied, and only irrelevant interactions re-
main. It is argued in this presentation that such a fermionic liquid, which we pro-
pose to call the quasi-Fermi liquid, exhibits the properties of both the Tomonaga-
Luttinger liquid and the Fermi liquid. Similar to the Tomonaga-Luttinger liquid,
the quasi-Fermi liquid does not support the inite-momentum quasiparticles; on
the other hand, the fermion occupation number demonstrates inite discontinuity
at the Fermi energy, which is a hallmark feature of the Fermi liquid. A possibility
of realizing the quasi-Fermi liquid in trapped cold atoms is discussed.
Abstracts
46

Superconducting Hybrids: From Sandwiches to Planar Structures
Valery Ryazanov1,2
, T.E. Golikova1,3
, and V.V. Bolginov1,2
1
: Institute of Solid State Physics, RAS, Chernogolovka, Russia
2
: National University of Science and Technology ”MISiS”, Moscow, Russia
3
: Moscow Institute of Physics and Technology, Dolgoprudniy, Russia
Report time: see page 13; Contact e-mail: valery.ryazanov@gmail.com
Josephson hybrids based on superconductors (S), normal metals (N) and ferro-
magnets (F) attract increasing attention in the last decade [1-7]. The most interest-
ing and important observations were made mainly on S/F/S and S/F/N/S sand-
wiches [3-7]. Among them it should be noted the implementation of �-junction
(superconducting phase inverter) [3-5], observation of the spin-triplet supercon-
ductivity [6], realization of SFS switches for ultra-low-power, high-density cryo-
genic memorie [7,8]. Modern fundamental and applied researches make the ac-
tual implementation and study of planar multiterminal S/F/N structures. Planar
Josephson S-(F/N)-S structures with complex bilayered (F/N) barriers were pro-
posed recently in [9] and realized in [10]. The structure, which we studied in [10],
included a Cu/Fe bilayer forming a bridge between two superconducting Al elec-
trodes. The appreciable critical current was detected up to 120 nm of the bridge
length. It was observed a double-peak peculiarity in diferential resistance of the
S-(N/F)-S structures at a bias voltage corresponding to the superconducting mini-
gap. The splitting of the minigap was explained by the electron spin polarization
in the normal metal which was induced by the neighbouring ferromagnet. Our
new observations are related to quasiparticle and spin-injection to banks and bar-
riers of planar Josephson junctions. First results were published in [11].
References:
1. A. A. Golubov, M. Yu. Kupriyanov, and E. Il’ichev, Rev. Mod. Phys. 76, 411
(2004).
2. A. I. Buzdin, Rev. Mod. Phys. 77, 935 (2005).
3. V.V. Ryazanov, V. A. Oboznov, A.Yu. Rusanov, A.V. Veretennikov, A.A.
Golubov, and J. Aarts, Phys. Rev. Lett. 86, 2427 (2001).
4. T. Kontos, M. Aprili, J. Lesueur, F. Genet, B. Stephanidis, and R. Boursier,
Phys. Rev. Lett. 89, 137007 (2002).
5. V. A. Oboznov, V. V. Bolginov, A. K. Feofanov, V. V. Ryazanov, and A. I.
Buzdin, Phys. Rev. Lett. 96, 197003 (2006).
6. T. S. Khaire, M. A. Khasawneh, W. P. Pratt, Jr., and N. O. Birge, Phys. Rev.
Lett. 104, 137002 (2010).
7. T. I. Larkin, V. V. Bol’ginov, V. S. Stolyarov, V. V. Ryazanov, I. V. Vernik, S. K.
Tolpygo, O. A. Mukhanov, Appl. Phys. Lett. 100, 222601 (2012).
Abstracts
47

8. B. Baek, W. H. Rippard, S. P. Benz, S. E. Russek, and P. D. Dresselhaus, Nat.
Commun. 5, 3888 (2014).
9. T. Yu. Karminskaya, A. A. Golubov, M. Yu. Kupriyanov, and A. S. Sidorenko,
Phys. Rev. B 81, 214518 (2010).
10. T. E. Golikova, F. Hübler, D. Beckmann, I. E. Batov, T. Yu. Karminskaya, M.
Yu. Kupriyanov, A. A. Golubov, and V. V. Ryazanov. Phys. Rev. B 86, 064416
(2012).
11. T. E. Golikova, M. J. Wolf, D. Beckmann, I. E. Batov, I. V. Bobkova, A. M.
Bobkov, and V. V. Ryazanov, Phys. Rev. B 89, 104507 (2014).
Long–Range Singlet Josephson Spin–Valve Efect in Ballistic
SFS Junction
Alexey Samokhvalov1
, R. I. Shekhter2
, A. I. Buzdin3
1
: Institute for Physics of Microstructures RAS, GSP-105, Nizhny Novgorod, Russia
2
: Department of Physics, University of Gothenburg, SE-412 96 Göteborg, Sweden
3
: Universit’e Bordeaux I, LOMA, UMR 5798, F-33400 Talence, France
Report time: see page 9; Contact e-mail: samokh@ipm.sci-nnov.ru
We suggest a new way of control of the singlet Cooper pairs low through a su-
perconductor/ferromagnet/superconductor (SFS) junction in the ballistic regime
[1]. The method consists in creation of thin non-collinear domain ∼ �ℎ ≪ �
(�ℎ � ℏ��ℎ) of the exchange ield ℎ near the center of a ferromagnetic weak link
using a magnetic tip/probe (see Fig. 1).
Fig. 1: The schematic sketch
of the SFS constriction under consideration: normal metal ballistic nanowire
(NW) in contac with a superconductor (S) and a ferromagnetic insulator (FI).
The ield domain generated by the probe, induces a special scattering of Cooper
pairs which corresponds to the spin-lip transition of electrons forming a pair. As
a result the scattered pair has a reversed spin arrangement with respect to the
Abstracts
48

ixed exchange ield, and reversed total momentum. At a symmetric domain
position ( ≃ ) the total phase gain � between the electron- and hole-like parts
of the wave function should be cancelled (� ∼ ( − )��ℎ → �) and the long–
range singlet Josephson transport in SFS link becomes possible. It means that the
presence of a small region with a non-collinear exchange ield near the center of a
ferromagnetic weak link restores the critical current inherent to the normal metal.
The long–range Josephson current (�) � sin �+ sin �� is very sensitive
to the position of the central domain, and the amplitude is negative at � .
This means that the spin-lip scatterer produces the �-shift efect and generates
a �-Josephson junction. With a displacement of the domain the SFS junction
can be switched from � to � state (Fig. 2).
Fig. 2: The dependence of the long-range amplitudes of the irst
(solid line) and the second (dashed line) harmonics of the current–phase
relation (�) on the shift � ( − )�� of the central domain with respect to
the weak link center. Dotted line shows the value of in absence of domain
The long–range behavior can be observed for a second harmonic in the current–
phase relation (�) as well. Certainly, the contribution of the second harmonic
in the current–phase relation (�) is small, except very close to the � − � transi-
tion ( � �). At this � − � transition the contribution of the second harmonic
becomes dominant. For all considered cases we obtained the positive amplitude
of the second harmonic in the vicinity of these transitions, which means that they
occur discontiguously by a jump between �− and �− phase states. The above phe-
nomenon opens a way to control singlet Josephson current through ballistic SFS
junction. An additional functionality of the considered device can be achieved by
electric biasing of the magnetic gate via the ield efect.
This work was supported, in part, by French ANR grant ”MASH” and by the
Russian Foundation for Basic Research (15-02-04116a).
References:
1. A.V. Samokhvalov, R.I. Shekhter, A.I. Buzdin, Scientic Reports 4, 5671 (2014)
Abstracts
49

Modeling of Intrinsic Josephson Junctions in High Temperature
Superconductors
Yury Shukrinov
BLTP, Joint Institute for Nuclear Research, and Dubna International University of Nature,
Society, and Man, Dubna, Russia
Report time: see page 3; Contact e-mail: shukrinv@theor.jinr.ru
Short review of our recent results on modeling of Josephson junctions in high
temperature superconductors are presented. Particularly, a variation of longitudi-
nal plasma wavelength under external electromagnetic radiation [1] and its exper-
imental testing is discussed. We demonstrate the principal diference in the reac-
tion of the system of coupled junctions to the external radiation in compare with a
case of single Josephson junction [2,3]. The IV-characteristics of a Josephson junc-
tion under external electromagnetic radiation show the devil’s staircase within
diferent bias current intervals [4,5]. It is found that the observed steps form very
precisely continued fractions. We discuss an algorithm for the appearance and
detection of subharmonics with increasing radiation amplitude and demonstrate
that the staircase structures registered in many well-known experiments and by
simulations form also the continued fractions. We study an efect of external ra-
diation on the dynamics of Josephson junction shunted by an LC circuit. When
the Josephson frequency is equal to the frequency of the circuit, additional stable
resonant circuit branches appear in the IV -characteristic of the junction. We show
that the amplitude dependence of the Shapiro step width crucially changes when
the Shapiro step is on the resonant circuit branch. These efects might give very
important advantages for methods and technologies that exploit the response of
Josephson junctions to microwave ields [6].
References:
1. Yu. M. Shukrinov, I. R. Rahmonov, M. A. Gaafar - Phys. Rev. B, 86, 184502
(2012).
2. Yu. M. Shukrinov and H. Abdelhaiz- JETP Letters, 98, 551 (2013).
3. Yu. M. Shukrinov, H. Azemtsa-Donfack, À.E. Botha. - Pisma v ZhETF, 101,
269 (2015).
4. Yu. M. Shukrinov, S. Yu. Medvedeva, A. E. Botha, M. R. Kolahchi, A. Irie -
Phys. Rev. B, 88, 214515 (2013).
5. Yu. M. Shukrinov, A. E. Botha, S. Yu. Medvedeva, M. R. Kolahchi, A. Irie -
Chaos, 24, 033115 (2014).
6. Yu. M. Shukrinov, I. R. Rahmonov, K. V. Kulikov, P. Seidel - EPL, 110 , 47001
(2015).
Abstracts
50

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