Akselrod article 3


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Это идея навязать фундаметальные резонансные частоты
колебаний фононов и/или их гармоники в известном
гелиевом сверхпроводнике другому материалу с очень
гибкой структурой

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Akselrod article 3

  1. 1. Akselrod Gennady Semenovich Induction of superconductivity at high- temperatures in a film of a two-layer covering by the method of laser dot impulse action on a known superconducting film The summary It is described experiment, connected with transfer exchange phonons from a film known gel superconductor in a film of a potential high-temperature superconductor. The method is based on earlier described mechanism of superconductivity as resonant character electron-phonon interactions in superconductors. Phonons, demanded frequencies in a film known (gel) superconductor are raised by a method of laser dot impulse action. It is supposed, that these phonons with fundamental frequency can create in the second film bosonic condensate with high critical temperature. Introduction Theory BCS gives a correct quantitative and qualitative picture of the mechanism of superconductivity by gel and nitric temperatures. But neither theory BCS, nor two-liquid model Landau-Ginzburg do not give concrete instructions how to receive superconductors with high (room) critical temperature Tc. The purpose of the given work is the description and a methodical substantiation of experiment on reception of a superconductor with high (room) temperature Tc. It is postulated, that there is a certain fundamental frequency exchange phonons (and multiple to it) with which help only and turn out superconducting cooper pairs. It follows from earlier described mechanism of superconductivity as resonant electron-phonon interactions. It is supposed, that phonons with such frequencies can appear in a potential superconductor at passage of phonons with terragerc frequencies through a known superconductor. In essence, it is attempt to bypass a limit imposed on critical temperature Tc by characteristic frequency of trimming Dω , corresponding Debye-frequency : /D D Dkβθ ω θ= × h . Critical temperature - that at which free energy of Gibbs for superconducting components becomes equal free energy of a normal condition. It is supposed, that 1
  2. 2. the experiment based on resonant character electron-phonon interaction can increase Dω by two order. I. The Basic idea of experiment 1.1. Formation of cooper pair electrons and an optimum configuration of an electromagnetic field in a superconductor probably only at fundamental (and multiple to them) frequencies of vibration exchange phonons at excitation in a superconductor of a superconducting current [1]: ( ) ( ) ( ) ( ) ( ) ( )0 0 01 0 1 0 1 2 2 /phq g T g T g T Eω ω× × ×= = h (1) Where ( )1phq ω - the minimum frequency of vibration exchange phonons in a superconductor at 0T = 0K; ( )0 1 2ω - The minimum frequency of vibration of cooper pair electrons at the flow in a superconductor of a superconducting current and 0T = 0K; ( )0 1 E - Energy of electrons in a superconductor at 0T = 0K; And ( )0 1 E = ( )0 0 0; / 2phqV Tξ ξ× ur h ( ) ( )0 01 sg T n T< ≤ , where ( )0g T - density of acoustic wave vectors of vibration of phonons, responsible for an attraction between electrons (and only an integer); ( )0sn T - Density of cooper pair electrons at 0T =0K. phqV ur - Speed and a direction virtual phonons, vibration with frequency ( )1phq ω at 0T =0K. 0ξ - Length of coherence (correlations) at 0T =0K. Consequence of this electron-phonon and electron-electronic resonant interaction in a superconductor superconductivity is possible only in the presence of a negative potential difference of a superconducting current [1]: ( ){ } ( ) 2 0 0 1 ' 0bq bq bq sE E E n T E− = − = − × < (2) 1.2. Technologically experiment consists that the two-layer vacuum covering is deposited on a substrate:the known gel superconductor and a potential high- temperature superconductor. It is known, that frequencies of vibration exchange phonons in a superconductor have an order terragerc frequencies. On the other hand, at 0K in known gel superconductor are involved all phonons fundamental terragerc frequencies. The idea of experiment consists in creating in gel superconductor superfluous phonons of terragerc or multiple frequencies to them. It can be made, influencing on this superconductor, for example, by a beam of the pulse laser (nano - or picoseconds). 2
  3. 3. Resounding with phonons of gel superconductor, these phonons can get sizes and harmonics of fundamental frequencies and to be transported in a potential high- temperature superconductor. These "donor" phonons can create cooper pair electrons and a necessary configuration of an electromagnetic field in a potential superconductor. Such potential superconductor should have very strong and simultaneously metastable ionic lattice. Metastability can help flexible to react on phonons of very high frequencies and, hence, to keep superconductivity at a high temperatures. [2] In other words, from the engineering point of view and according to (2), in a potential superconductor there should be a negative potential difference of an induced current. Then the configuration of the electromagnetic field created by this electric tension, can transform the induced current into the superconducting. II. The experiment scheme Experiment is offered to construct as follows (two variants): 1)The known gel superconductor NbGe thin film is deposited on ceramic substrate.Form of film- a ring with an appendix. From above is deposited the thin film of refractory multicomponent alloy ЭИ-893, also the ring form, but without an appendix . The thickness of film ЭИ-893 varies - from 30 o Α to 1000 o Α. A method of drawing of both films is a vacuum dusting Right after dusting,each film is processed in the same vacuum chamber by the glow discharde in argon atmosphere at a gas pressure of~ (2∙10-2 ÷10-3 ) Torr.This is necessary in order to improve the quality of adhesion of thin films on the subrate.2) the same films are deposited on the internal surface of the polished glass tube. It is simple for making with the help of the Penning's magnetron. In this variant is possible to receive qualitatively other results. However, here it is required to consider too strong and difficult influence of a magnetic field. Therefore in this work we will consider only the first variant. As tool backup of experiment serve: 1) liquid helium; 2) pulse (nano - or piko-) the second laser; 3) the computer. The computer is connected with the laser and film ЭИ-893 of a straight line and return coupling. Сeramized substrate with coverings is located in capacity with liquid helium and is cooled to temperature close to zero of degrees of Calvin. Then the superconducting current is induced in film Nb3Ge. Accordingly, and in film ЭИ- 893 the ring current which can heat up film Nb3Ge to the temperature close to the critical is induced. Therefore influence on an appendix of film Nb3Ge of dot pulse laser heating practically simultaneously begins. The laser beam lasts ~200 nanoseconds and gives on a film surface warm stain in the size about 100 microns and with temperature to 20K. [3] 3
  4. 4. It is also critically moment as if the temperature of film Nb3Ge exceed critical, will interrupt a superconducting current. The beam of the pulse laser raises in film Nb3Ge of phonons of terragerts frequencies [3] that can lead to effect of high- temperature superconductivity in film ЭИ-893 as it is described above. Overcoming of this critical moment is experiment grain. In the computer is put the certain program . According to it, if there is in a film of alloy ЭИ-893 a superconducting current, the computer simultaneously will allow a command to the laser to stop impulses. When liquid helium evaporate, it will be clear, whether is the film of alloy ЭИ-893 a superconductor with critical temperature of an order room. III. The Substantiation of a choice of materials, two-layer thin-film system and a configuration of surfaces 3.1. The choice as known gel a superconductor of film Nb3Ge is caused by that this superconductor possesses the highest critical temperature (23,2K) from known gel superconductors. This very important circumstance if to consider the critical moment specified in item II. Besides, the thin film from material Nb3Ge is offered a priori as superconductivity with Tc = 23,2К is received in a thin vacuum film from this material. As a potential superconductor the thin film from refractory multicomponent alloy ЭИ-893 is offered. It is connected with two factors. First, the alloy has very strong basic ionic lattice of type wursmit (Ni-65%, Cr- 15%), but thanks to a considerable quantity of additional elements (10 elements - 20 %) this ionic lattice is metastable. [4] Exactly in such structures, by application of the magnetic is expected the formation of lattice of quantized circulation of filamentary vortex, demanding for stabilisation «creep stream» of some thermal activation . [5] Secondly, it is connected with experiments which were done by the author: 1) The thin film of alloy ЭИ-893 of the ring form, thickness ≈1000 o Α, after drawing on a quartz substrate had electric resistance ~300 Ohm. After annealing on atmosphere, at Тannealing≈1000 o C on a film colours of bluing, characteristic for the oxidised metal were formed. However, electric resistance of film ЭИ-893 fell to 180 Ohm. 2) The thin film of alloy ЭИ-893 from 30 o Α to 100 o Α (within an error of measurements) was put by thickness on сeramized substrate. The film had a strip 4
  5. 5. configuration; as contact electrodes thin films from iridium (Ir) served. The system has passed multi-stage annealing (300 o C; 550 o C; 700 o C; 1000 o C); after every annealing was measured electric resistance of a strip . Before the first annealing the strip had characteristic metal shine; electric resistance before the first annealing was equalled 300 Ohm. As far as annealing the film all became more transparent, but its electric resistance steadily went down. After annealing at 700 o C the film became absolutely transparent, i.e. on appearance unequivocally looked as dielectric from the oxidised metal - however, its electric resistance has fallen to 30 Ohm. After annealing at 1000 ℃ the film has completely evaporated, and resistance between iridic electrodes became equally electric resistance of polycrystalline glass (~1013 ÷1014 the Ohm). Thus, the film from alloy ЭИ-893 is offered the author on the basis of instructions of theorists that high-temperature superconductors should lower the electric resistance with temperature growth. [6], [7] 3.2. As it is specified in item 1.2., the basic idea of experiment consists in transportation exchange virtual phonons of certain frequencies from known ge superconductor in a potential high-temperature superconductor. Thus very important role is played by possibility of penetration acoustic phonons from one material in another. Such possibility outright depends on a parity of density of both materials. The above the material density in which should be transported phonons, in comparison with density of material-source of phonons, so much less probability of penetration of phonons through border of section of both materials. [8], [12] Usually in the thin films received by a vacuum dusting, the density has very much a neighbour; anyway, for this purpose there are many technological possibilities. For this reason in the given work the vacuum two-layer thin-film covering with approximately identical density of each layer is offered. 3.3. The experiment technique basically is focused on superconductors of 2nd sort, from an irreversible curve of magnetisation. At the application of an external magnetic field for such superconductors is characterised the formation of the lattice of quantized circulation of filamentary superconducting whirlwinds with some thermal activation (and in such superconductors, under condition of stabilisation of this lattice, it is expected high-temperature superconductivity [9], [10]) In the given work for this reason the ring form of known and potential superconductors is offered. The superconducting current in Nb3Ge induces a ring current in ЭИ-893, that is equivalent to the application an external magnetic field to a known superconductor. If in film ЭИ-893 appears a high-temperature superconducting current it will already induce a ring current in film Nb3Ge, that just as is equivalent to the magnetic field application already to a high-temperature superconductor. The ring current, heating up superconductors, in both cases 5
  6. 6. provides stabilisation of processes of pinning and creep streams (thermal activation). The area of coverings gets out from the point of view of squares of the areas as it is described in the work [11]. For example, if the area of a film known gel superconductor Nb3Ge makes 1sm2 , and (1) 23,2sT K= , that, having assumed for film ЭИ-893 (2) 300sT K= , we have: |300|= ( )4 (2) 300 23,2 1b sm Rρ ρ ∆= × − × + × where ρ and b - table values, and it is easy to calculate (2) R∆ [sm4 ] and, accordingly, (2) R∆ , i.e. the demanded area [sm2 ] films of potential superconductor ЭИ-893. IV. The substantiation of application of laser dot pulse heating and calculation of parameters of experiment The method of dot pulse laser heating gives following possibilities for reception of effect of high-temperature superconductivity in two-layer thin-film system for a potential superconductor from a thin film of multicomponent refractory alloy ЭИ- 893. 4.1. We will consider the minimum energy resonant electron-phonon interactions in a superconductor at flow in it of a superconducting current (at 0K) [1]: (1) (1) 0(1) 0 | | ' 2 2 phq phq bq V E E ω ξ = = × = × ur h h (3) Where (1)'bqE - the minimum energy of exchange phonons in cooper pair; 0(1)E - The minimum energy of electron at 0K in a superconductor; h - Planck's constant; 0ξ - Length of correlation; phqV ur - Speed exchange of phonons in a superconductor (1)phqω - The minimum frequency of fluctuations of exchange phonons in a superconductor From (3) can follow, that superconductivity realisation as resonant condition depends not only on size phqV ur , but also from a direction of this vector. On the other hand, at dot pulse laser heating speed of an acoustic wave ( ) ( ) /V k k kω= ur r r (4) Depends only on a direction of vector k r , and does not depend on its size. [3] 6
  7. 7. It is possible to say about identity of vectors phqV ur and ( )V k ur r , that follows from (3) and (4). It is supposed, that the allocated directions acoustic phonons of terragerts frequencies in 4 pulse space of co-ordinates, in relation to a direction of speed of distribution of an electronic superconducting condensate are an obligatory condition of occurrence electron-phonon interactions. Thus, the method of dot pulse laser influence serves not only way, but also the mechanism of induction to superconductivity in a thin film of alloy ЭИ-893 as certain frequencies and directions phonon vectors appear only after passage of impulses through known gel superconductor Nb3Ge. 4.2. It is important to notice, that at 0T =0K. (and it is close to experiment entry conditions) are involved all electrons and phonons of the certain frequencies, participating in electron-phonon interaction (i.e. participating in a superconducting current). [1] Therefore phonons with the same frequencies are not so necessary to superconductor Nb3Ge, and they can be transported in film ЭИ-893. From this follows, that phonons with such frequencies can stimulate occurrence of the power conditions favourable to formation of cooper pair electrons in the induced superconductor (from the point of view of minimisation of free Gibb's energy). 4.3. It is possible to count parameters of laser dot impulsive heating for offered technology. We will consider the formula: ( )b phE g T ω= × ×h [1] (5) Where bE - an energy part electron-phonon interactions, responsible for an attraction between electrons; T - Superconductor temperature; phω - Frequency of vibration virtual exchange phonons; ( )g T - Density of acoustic wave vectors ( )k T r of vibration of phonons, responsible for an attraction between electrons. In the formula (5) frequencies phω having density of wave vectors ( ){ }g k T are defined from following reasons. The equation of movement ballistic phonons for crystals with cubic symmetry (as at Nb3Ge and ЭИ-893) registers in a kind of tensors of elasticity's modules: 2 i is ijml m l w w C x x ς ∂ = ∂ ∂ [3] (6) Where sς - density of medium (a superconducting material in our case); iw - A vector of displacement of an element of volume from balance position. The equation (6) has the wave decision: ( ){ }expph phw i kx tε ω= × − × rr [3] (7) Where phε - amplitude of energy of vibration of phonons; t - the period of fluctuations (time); x r - Displacement on axes of co-ordinates. 7
  8. 8. According to [1] we will consider the formula: ( ) ( ){ } ( ) 2 (1) 0 0 0 0 1 ;bq sE T n T Eξ′ = × (8) To count initial parameters of the experiment it is supposed proceeding from formulas (3) and (7), substituting value ( )1phqω in (7): ( ) ( ) 2 0 0 0 exp 2 s phqph n T w i k T x V tε ξ       = × × × − × ×       r r ur h (9) As it is specified in [3], it assumes formation under the influence of an impulse, square-law dependence of density virtual phonons from temperature. If to address to the formula (8) again it is possible to underline, that the way and the mechanism of stimulation of high-temperature superconductivity grow together. 4.4. Time of passage ballistic phonons through a thin film of a known superconductor very little. We will try to estimate it. The speed of phonons of terragerts frequencies in crystals of cubic symmetry, depending on type of an elastic fashion and a distribution direction in relation to symmetry axes, changes from 3,0∙105 sm/s to 6,6∙105 sm/s. [3] Let's accept, as a first approximation, for average speed | |V ur ≈ 5∙105 sm/s. The thickness (d) a thin film has an order ≈10-5 sm. Usually measured times of flight appear simply equal (d/v). Hence, t ≈ 0,2∙10-10 s, that coincides in the order of size with a constant of time of the electromagnetic response (10-10 s). Thus, if to consider, that influence of a laser beam lasts ≈ 200ns [3] at one impulse 104 variants of construction of a necessary configuration of an electromagnetic field with a minimum of the free energy necessary for construction of cooper pair electrons are fulfilled. Using an irradiation on an appendix, it is possible to raise influence time on (1÷2) an order. Such are technological possibilities of a method for increase of probability of stimulation resonant electron-phonon interactions in a potential superconductor from a film of material ЭИ-893. [4] IV. Conclusions 5.1. Experiment on reception of a superconductor with high critical temperature in a two-layer vacuum covering is described and methodically proved. As known (gel) a superconductor the vacuum-raised dust film is chosen from material Nb3Ge; as a potential high-temperature superconductor is chosen the vacuum-raised dust film from multicomponent alloy ЭИ-893. 5.2. Injecting donor phonons of terra - or pikogerc frequencies from a film of a known superconductor in a film of a potential superconductor, at flow in them of a current it is possible to create such configuration of an electromagnetic field in a potential superconductor at which the high-temperature superconducting current can be induced. 8
  9. 9. It is shown, that the most comprehensible to offered experiment are thin vacuum films. It is connected by that in such two-layer covering is simple to achieve close density on size of both films, and it does by the most transparent border for above- stated donor phonons. 5.3. As the generator transported donor phonons the method of laser pulse dot influence on known (gel) superconductor is chosen. Using pulse terra - or picoseconds laser, it is possible to create phonons demanded frequencies. Passing through known (gel) superconductor these phonons get not only certain frequencies (and harmonics of frequencies), but also the certain vector directions, demanded for creation a necessary electromagnetic field in a potential superconductor. 5.4. It is proved ring figuration a two-layer covering from known and potential superconductors. It in both cases to similarly appendix of an external magnetic field since the way is focused on superconductors of 2nd sort from an irreversible curve of magnetisation, and demanding some thermal activation for stabilisation of creep and pining's stream of quantized whirlwinds of superconducting threads. From the technological point of view necessity of presence of a shoot at known (gel) superconductor is shown. 5.5. It is shown, that experiment ( the influence by laser on the shoot of a known superconductor) should be begun influence by the laser with the temperature of coverings close to 0K. It is experiment grain. 5.6. It is shown, how it is possible to count initial parameters of experiment: the formula (9). It is shown as, what possibilities (quantity of variants ~106 ) for achievement of high-temperature superconductivity in a potential superconductor at unitary influence of a pulse laser beam terraseconds laser. The literature [1] G.S.Axelrod «Electricy tension of a superconducting current at extreme temperatures» [2] E.M.Savitsky «Research and application of alloys of refractory metals». Moscow, 1983 [3] «Physics abroad». The collection of popular scientific articles//J. Volf «Ballistic thermal impulses in crystals». Moscow, 1982 9
  10. 10. [4] Alloy ЭИ-893 «ТУ 14-1-2481-78» (rod ХН65ВМТЮ-ВД) [5] D.R.Tilli, J. Tilli «Superfluidity and superconductivity». Moscow, 1977 [6] «The superconductivity Theory» the Collection of articles. Moscow: Publishing house of the foreign literature, 1960 [7] L.N.Bulaevsky, etc. «The problem of high-temperature superconductivity». Moscow, 1977 [8] S.V.Birjukov «Superficial acoustic waves in non-uniform environments». Moscow: the Science, 1990 [9] S.V.Vonsovsky «Superconductivity of transitive metals, their alloys and connections». Moscow, 1977 [10] B.T.Gejlikman, etc. «the Kinetic and non-stationary phenomena in superconductors». Moscow, 1972 [11] G.S.Akselrod «Empirical parameters for high-temperature superconductivity». [12] Magazine of experimental and theoretical physics, 1994, т.6, вып.3 (9), p. 828-847//V.I.Alshits, etc. «About superficial elastic waves on the loaded border of a crystal» 1