The document discusses electron-phonon renormalization of electronic band structure. It begins by introducing the concept of electrons and ions interacting together in a material. It then describes the Born-Oppenheimer approximation approach, which treats electron-phonon coupling perturbatively. This approach is used to calculate corrections to electronic energy levels and band structures due to electron-phonon interactions. The summary describes how this coupling affects key properties like band gaps, masses, and spectroscopic measurements in real materials like diamond and GaN.
I show how much GW corrections are important not only for the band structure but also in the calculation of the electron-phonon matrix elements. I present different examples and comparison with the experimental results.
BIOS203 Lecture 1: Introduction to potentials and minimizationbios203
Lecture 1 for BIOS 203 Mini-course at Stanford University taught by Heather J. Kulik. http://bios203.stanford.edu for more info or email bios203.course@gmail.com
I show how much GW corrections are important not only for the band structure but also in the calculation of the electron-phonon matrix elements. I present different examples and comparison with the experimental results.
BIOS203 Lecture 1: Introduction to potentials and minimizationbios203
Lecture 1 for BIOS 203 Mini-course at Stanford University taught by Heather J. Kulik. http://bios203.stanford.edu for more info or email bios203.course@gmail.com
In this work, the performances of a solar cell based on InGaN were simulated under the illumination conditions of one sun by employing SILVACO software.
Quantum mechanics for Engineering StudentsPraveen Vaidya
The Quantum mechanics study material gives insight into the fundamentals of the modern theory of physics related to Heisenberg uncertainty principle, wavefunction, concepts of potential well etc.
UCSD NANO 266 Quantum Mechanical Modelling of Materials and Nanostructures is a graduate class that provides students with a highly practical introduction to the application of first principles quantum mechanical simulations to model, understand and predict the properties of materials and nano-structures. The syllabus includes: a brief introduction to quantum mechanics and the Hartree-Fock and density functional theory (DFT) formulations; practical simulation considerations such as convergence, selection of the appropriate functional and parameters; interpretation of the results from simulations, including the limits of accuracy of each method. Several lab sessions provide students with hands-on experience in the conduct of simulations. A key aspect of the course is in the use of programming to facilitate calculations and analysis.
In computational physics and Quantum chemistry, the Hartree–Fock (HF) method also known as self consistent method is a method of approximation for the determination of the wave function and the energy of a quantum many-body system or many electron system in a stationary state
In this work, the performances of a solar cell based on InGaN were simulated under the illumination conditions of one sun by employing SILVACO software.
Quantum mechanics for Engineering StudentsPraveen Vaidya
The Quantum mechanics study material gives insight into the fundamentals of the modern theory of physics related to Heisenberg uncertainty principle, wavefunction, concepts of potential well etc.
UCSD NANO 266 Quantum Mechanical Modelling of Materials and Nanostructures is a graduate class that provides students with a highly practical introduction to the application of first principles quantum mechanical simulations to model, understand and predict the properties of materials and nano-structures. The syllabus includes: a brief introduction to quantum mechanics and the Hartree-Fock and density functional theory (DFT) formulations; practical simulation considerations such as convergence, selection of the appropriate functional and parameters; interpretation of the results from simulations, including the limits of accuracy of each method. Several lab sessions provide students with hands-on experience in the conduct of simulations. A key aspect of the course is in the use of programming to facilitate calculations and analysis.
In computational physics and Quantum chemistry, the Hartree–Fock (HF) method also known as self consistent method is a method of approximation for the determination of the wave function and the energy of a quantum many-body system or many electron system in a stationary state
UCSD NANO 266 Quantum Mechanical Modelling of Materials and Nanostructures is a graduate class that provides students with a highly practical introduction to the application of first principles quantum mechanical simulations to model, understand and predict the properties of materials and nano-structures. The syllabus includes: a brief introduction to quantum mechanics and the Hartree-Fock and density functional theory (DFT) formulations; practical simulation considerations such as convergence, selection of the appropriate functional and parameters; interpretation of the results from simulations, including the limits of accuracy of each method. Several lab sessions provide students with hands-on experience in the conduct of simulations. A key aspect of the course is in the use of programming to facilitate calculations and analysis.
Phonon assisted Luminescence in Hexagonal Boron NitrideElena Cannuccia
Hexagonal Boron Nitride (hBN) as graphite is a lamellar compound. They share many physical properties and they can be exfoliated in monolayers for Van der Waals heterostructures. However a difference does exist, graphite is a gapless compound while hBN is a wide band gap material. In particular first principles calculations agree upon the existence of an indirect quasiparticle band gap: the conduction band minimum sits at the M point while the valence band maximum is around the K point of the Brillouin zone.
On the experimental side the nature of the electronic band structure of hBN has animated a long-standing debate. Pioneering works of Watanabe et al. [1] have revealed the high UV radiative efficiency of hBN at room temperature. He first came to the conclusion that hBN was driven by direct excitonic recombination. Recently Cassabois et al. instead explained the luminescence lines to phonon-assisted recombination from an indirect exciton. Aiming to describe phonon-assisted luminescence a theoretical formulation that combines electron-hole interactions and electron-phonon coupling is needed. In recent years the method of finite differences turned out to be a powerful tool to treat the electron-phonon coupling in a perturbative way. So we combine Green’s function theory with finite difference electron-phonon coupling to get an accurate description of the phonon assisted luminescence spectrum of hBN.
Phonon-assisted luminescence in Hexagonal Boron NitrideElena Cannuccia
Hexagonal Boron Nitride is a wide band gap material. In particular first principles calculations agree upon the existence of an indirect quasiparticle band gap : the conduction band minimum sits at the M point while the valence band maximum is around the K point of the Brillouin zone. On the experimental side the nature of the electronic band structure of hBN has animated a long-standing debate. Pioneering works of Watanabe et al. [1] have revealed the high UV radiative efficiency of hBN at room temperature. He first came to the conclusion that hBN was driven by direct excitonic recombination. Recently Cassabois et al. [2] instead explained the luminescence lines to phonon-assisted recombination from an indirect exciton. Aiming to describe phonon-assisted luminescence a theoretical formulation that combines electron-hole interactions and electron-phonon coupling is needed. In recent years the method of finite differences [3] turned out to be a powerful tool to treat the electron-phonon coupling in a perturbative way. So we combine Green’s function theory with finite difference electron-phonon coupling to get to an accurate description of the phonon assisted luminescence spectrum of hBN.
[1] Watanabe et al. Nature Materials 3, 404 (2004)
[2] Cassabois et al. Nature Photonics, 10, 262 (2016)
[3] B. Monserrat, Journal of Physics: Condensed Matter 30, 083001 (2018)
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
Introduction to AI for Nonprofits with Tapp NetworkTechSoup
Dive into the world of AI! Experts Jon Hill and Tareq Monaur will guide you through AI's role in enhancing nonprofit websites and basic marketing strategies, making it easy to understand and apply.
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Macroeconomics- Movie Location
This will be used as part of your Personal Professional Portfolio once graded.
Objective:
Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
Unit 8 - Information and Communication Technology (Paper I).pdf
Introduction to the electron-phonon renormalization of electronic band structure
1. Introduction to theIntroduction to the
electron-phononelectron-phonon
renormalization ofrenormalization of
electronic band structureelectronic band structure
2. Electron phonon renormalizationElectron phonon renormalization
of electronic band structureof electronic band structure
The N particlesThe N particles
world:world:
ionsions andand electronelectronss
all togetherall together
4. The separated worlds ofThe separated worlds of
phonons and electronphonons and electronss
Electrons live in the bands
generated by the ionic potential
Phonons are the quantized
ionic vibrations on the potential
generated by the electrons
6. ARPES: direct method toARPES: direct method to
photograph the electronicphotograph the electronic
structure of surfaces 1/3structure of surfaces 1/3
7. ARPES: direct method toARPES: direct method to
photograph the electronicphotograph the electronic
structure of surfaces 2/3structure of surfaces 2/3
8. ARPES: direct method toARPES: direct method to
photograph the electronicphotograph the electronic
structure of surfaces 3/3structure of surfaces 3/3
12. Coupling electrons and phononsCoupling electrons and phonons
……
Superconductivity
Joule's heating
Electron relaxation
(luminescence)
Polaronic transport
Coherent Phonons
Peierls instability
Raman Spectroscopy
etc......
13. EPC on the electronicEPC on the electronic
structurestructure
Kink in the band structure
Mass Enhancement
Temperature dependence of
band gaps
A. Marini, PRL 101,106405 (2008)
14. Energy levels renormalizationEnergy levels renormalization
ThermalThermal
expansionexpansion
Electron-PhononElectron-Phonon
interactioninteraction
P.B. Allen and M. Cardona Phys. Rev. B 27 4760 (1983)
>>
Where does the coupling come from?
16. A perturbative approach:A perturbative approach:
Heine-Allen-Cardona 1/2Heine-Allen-Cardona 1/2
For a review see M. Cardona,
Solid State Commun. 133, 3 (2005).
H (x+u)=H (x) +
∂V scf
∂ x
u +
1
2
∂2
V scf
∂ x
2
u2
+...
Using
Perturbation TheoryPerturbation Theory,
we get the correction
to the energy
δ Ei=〈Ψi
(0)
∣ ∣Ψi
(0)
〉 + 〈Ψi
(0)
∣ ∣Ψi
(0)
〉 + 〈Ψi
(0)
∣ ∣Ψi
(1)
〉 +...
First order PT Second order PT
V scf (x+u)=V scf (x) +
∂V scf
∂ x
u +
1
2
∂2
V scf
∂ x2
u
2
+....
17. A perturbative approach:A perturbative approach:
Heine-Allen-Cardona 2/2Heine-Allen-Cardona 2/2
Debye-Waller Fan
δ Ei(β) = [
1
2
〈
∂
2
V scf
∂ x2
〉 + ∑j
(Ei−Ej)
−1
〈
∂V scf
∂ x
∣j〉〈 j∣
∂V scf
∂ x
〉] 〈u
2
〉
Clear dependence on the
Temperature
B(w) = Bose function
δ En k (β)=∑q λ n'
[
|gnn' k
q λ
|
2
En k−En' k+q
−
Λnn' k
q λ
En k−En' k
](2B(ωq λ)+1)
Thermal average
Average on the
electronic
wavefunction
FINAL FORMULA
19. The gap of diamondThe gap of diamond
(1/2)(1/2)
F. Giustino, et al. PRL, 105, 265501 (2010)
E. Cannuccia, Phys. Rev. Lett. 107, 255501 (2011)
Logothedis et al. PRB 46, 4483 (1992)
Electronic Gap: 7.715 eV
Renormalization: ~700 meV
Classicalions
20. The gap of diamondThe gap of diamond
(2/2)(2/2)
Exp: Logothetidis et al.
PRB 46, 4483 (1992)
Quantum (PI)
MD calculations
Ramirez et al. PRB 73, 245202 (2006)
21. Isotopic EffectsIsotopic Effects
〈u
2
〉=〈
h
4Mω
{2[e
−hω/KT
−1]
−1
+1}〉
At high T,
independent of M (classical effect)
At low T,
zero point vibrations (quantum)
〈u
2
〉∝KT
〈u
2
〉∝M
−1/2
The quantisticThe quantistic
zero-pointzero-point
motion effectmotion effect
Parks et al. PRB 49,14244 (1994)
Eg
M
M→∞Eg electronic
23. Finite temperature electronic and opticalFinite temperature electronic and optical
properties of zb-GaNproperties of zb-GaN
H. Kawai, K. Yamashita, E. Cannuccia, A. Marini
Phys. Rev. B. 89, 085202 (2014)
BroadeningBroadening induced
by electron-phonon
scattering and
temperature
dependence
24. Results: electronic band structureResults: electronic band structure
Breakdown ofBreakdown of
the QP picturethe QP picture
E. Cannuccia and A. MariniE. Cannuccia and A. Marini
Europ. Phys. J. B.Europ. Phys. J. B. 8585, 320 (2012), 320 (2012)
H e' quella elettronica della DFT.
Fermiarmi al 2 ordine → expansione armonica significa assumere che le frquenze fononiche non dipendono dal volume del cristallo, quindi non sto tenendo conto di effetti anarmonici che sono legati all'expansione termica.
C, N, O
.. have no p-electrons in the core and the p valence electrons, as the atoms vibrate, can get much closer to the core than in cases where p-electrons
are present in the core: germanium, silicon, GaAs….
The dipendence of the gap at high temperatures is linear and then it deviates because of quantum effects. Classically the gap correction is equal to zero, than at T=0 the intersection yields the electronic gap.