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1.
The existence of two solutions for proximity-induced superconductivity described by the Ginzburg-Landau theory is established in the general case. A first-order phase transition can occur between these states, resulting in superconductive wetting. 相似文献
2.
Prange RE 《Physical review letters》2003,90(7):070401
In quasiclassical spectral theory, "resurgence" means that long periodic orbits can be expressed by short ones in such a way that the spectral determinant is real. The question has thus long been posed whether long scattering orbits can be expressed by short orbits in such a way as to make the quasiclassical scattering matrix unitary. We here find a resurgent and manifestly Hermitean expression for Wigner's R matrix, implying a unitary scattering matrix. The result is particularly important if the average resonance width is comparable with the average resonance spacing. 相似文献
3.
The amplitude of scattering of f electrons has been calculated for the periodic Anderson model in the strong-correlation limit (U = ∞) in the Cooper channel. From the condition of the existence of a pole of this amplitude, an equation is derived for determining the critical temperature (T c) of the transition to the superconducting phase with the s symmetry of the order parameter. The temperature T c as a function of the electron density and hybridization parameter has been calculated by self-consistently solving the system of equations. The region of the existence of the superconducting phase is found to adjoin the region of the existence of the unsaturated ferromagnetic state and does not overlap it. The results can be used to describe the transition to the superconducting phase with the s symmetry of the order parameter in heavy-fermion skutterudite LaFe4P12. In this case, the inclusion of the scattering of fermions by spin fluctuations turns out to be substantial enough to obtain T c values close to the experimental data. 相似文献
4.
R. O. Zaitsev 《JETP Letters》2004,79(3):113-116
The concept of spin fluctuations in the Hubbard model is used for deriving a closed system of equations for the superconducting order parameter Δ and spin susceptibility. The limiting cases of low temperatures and temperatures close to the superconducting transition temperature are considered. The temperature dependences of the parameter Δ and the Knight shift are obtained. The conditions under which the second-order phase transition turns to the first-order phase transition are established. 相似文献
5.
Summary The existence of pair excitations in a Fermi gas interacting via a short-range attractive potential is investigated. Within
the ladder approximation to the Bethe-Salpeter equation for the effective two-particle interaction, evidence of pair excitation
is found at energies slightly larger than the chemical potential. The link between those excitations and a boson-fermion model
of superconductivity (Phys. Lett. A,196 (1995) 359) is discussed. In particular it is shown that the charge carrier density dependence of the pair excitation (boson)
energy, assumed phenomenologically in the boson-fermion model, is consistent with the properties of the interacting Fermi
gas studied. These results give support to the microscopic origin of the phenomenological boson-fermion model of superconductivity.
Within the polaron-bipolaron theory the assumption that bosons and fermions can be described as mobile particles has found
support in ref.[6] where the small bipolaron (boson) delocalization is discussed and in ref.[7] where the large polaron delocalization
is analysed. 相似文献
6.
P. Esquinazi T. T. Heikkilä Y. V. Lysogorskiy D. A. Tayurskii G. E. Volovik 《JETP Letters》2014,100(5):336-339
We propose an explanation for the appearance of superconductivity at the interfaces of graphite with Bernal stacking order. A network of line defects with flat bands appears at the interfaces between two slightly twisted graphite structures. Due to the flat band the probability to find high temperature superconductivity at these quasi one-dimensional corridors is strongly enhanced. When the network of superconducting lines is dense it becomes effectively two-dimensional. The model provides an explanation for several reports on the observation of superconductivity up to room temperature in different oriented graphite samples, graphite powders as well as graphite-composite samples published in the past. 相似文献
7.
It is shown that an electron-hole liquid under suitable conditions can become superconducting. This conclusion is reached by using an effective electron-electron interaction which includes vertex corrections and multiple electron-hole scattering. The mechanism for superconductivity is novel. The intermediate bosons responsible for the superconducting pairing are not acoustic plasmons but correlated pair excitations from the Fermi sea of the holes. Some materials are proposed for an experimental verification of the ideas presented here. 相似文献
8.
M. V. Krasin’kova 《Technical Physics》1998,43(11):1347-1349
The question of the dimensionality of superconductivity is considered within the framework of a model of superconductivity
via asymmetric, delocalized “crystalline” π orbitals (analogous to the corresponding molecular orbitals) extending along chains of covalently bonded copper and oxygen
ions. It is shown that superconductivity is preceded by a separation of the bonds in the CuO2 layer into covalent and ionic bonds with ordering of the covalent bonds into chains. Such an ordering facilitates the formation
of a crystalline π orbital lowering the crystal energy by the resonance energy of the π bond and is therefore favored. The superconducting current is created by non-dissipative motion of π-electron pairs along the asymmetric, “crystalline” π orbitals extending along chains of covalently bonded copper and oxygen ions, in the presence of an ionic bond between neighboring
chains extending through the easily polarizable O2− ions. This ionic bond correlates the motion of the electron pairs along all the π orbitals and stabilizes the superconducting state. Only in this sense is the apparent “onedimensionality” of superconductivity
in cuprate superconductors to be understood.
Zh. Tekh. Fiz. 68, 82–84 (November 1998) 相似文献
9.
R. O. Zaitsev 《Journal of Experimental and Theoretical Physics》2011,113(5):857-872
The possibility of Cooper instability in transition metal compounds is established based of the concept of the strong interaction
in the same unit cell. The multicomponent scattering amplitude of excitations is calculated. The superconductivity equations
are derived for compounds of 3d transition metals. It is shown that in the pole approximation, the superconductivity equations can be reduced to the multicomponent
superconductivity equations with preset BCS constants. A method is developed for calculating one-orbital constants and constants
with different orbitals as functions of the total spin. The concentration ranges of superconducting ordering are obtained
for one-orbital equations. 相似文献
10.
R. O. Zaitsev 《JETP Letters》2001,74(1):15-19
It is established on the basis of a concept of strong coupling in a single unit cell that the Cooper instability can occur in a system with hopping between the cations and anions of transition and main-group elements. A phase diagram is constructed for the ferromagnetic ordering in the coordinates (h d , h p ) of the degrees of underfilling of, respectively, the 4d 10 and 2p 6 shells of transition and main-group elements. 相似文献
11.
Conductivity and superconductivity studies of amorphous [Sn1–y
Cu
y–]1–x
H
x
samples in connection with119Sn Mössbauer effect experiments on119Sn1–x
H
x
give strong evidence that the observed increase of the superconducting transition temperatureT
c in the Sn–H-system is caused by the stabilization of an amorphous structure. Thus the Sn–H-system is very similar to the Sn–Cu-system and no H-specific effect is needed to explain the increase ofT
c. 相似文献
12.
R. O. Zaitsev 《JETP Letters》2011,94(3):206-212
The possibility of the existence of Cooper instability in a system with hops between carbon anions that form a honeycomb lattice
has been established based on an idea about the strong interaction in one atom of the unit cell. The phase diagram of the
existence of the superconducting ordering and the BCS constant has been calculated for various filling factors of the π or
σ shell. 相似文献
13.
This article is a brief review of the present situation in theoretical investigations of high temperature superconductivity. The main subject is a discussion of the formula for a critical temperature Tc for a homogeneous and isotropic substance with arbitrary permeability ?(q, ω). The problem of the maximum possible value of Tc is discussed. It is concluded that at present there are no grounds to consider that values of Tc ? 100°K to be impossible. The paper ends with some remarks on the exciton mechanism of superconductivity for the case of superconductors with a plane geometry. 相似文献
14.
É. G. Batyev 《JETP Letters》2003,78(4):207-212
The disorder effect on the interaction of quasiparticles between each other is discussed. The occurrence of a soft mode is taken as the basic assumption. The interaction through the soft mode results in attraction between Fermi quasiparticles (this is apart from the repulsion that has remained from the initial Coulomb interaction between particles). This attraction (in the vicinity of the Fermi surface) is strengthened with increasing concentration of the scattering centers. Therefore, even if the pure system exhibits no superconductivity, superconductivity could appear in the impurity system. 相似文献
15.
An attempt is made to explain the occurrence of superconductivity in Kondo lattice systems with special reference to CeCu2Si2. Starting point is the Fermi liquid approach. It is generalized from a Kondo impurity to the Kondo lattice by means of the Korringa-Kohn-Rostocker method. From it a hybridization model is derived and discussed in detail. Two electron-phonon mechanisms are investigated which appear in Kondo lattices. One results from the additional phase shifts caused by the Kondo ions while the other is responsible for the so-called Kondo volume collapse. It is shown that the latter is sufficiently strong in order to explain why CeCu2Si2 is a superconductor while LaCu2Si2 is not. An estimate for the superconducting transition temperatureT
c produces the right order of magnitude. 相似文献
16.
Two high temperature beryllium allotropes have been stabilized at room temperature through the addition of transition elements. Superconductivity has been observed in almost all of them. Beryllium films reported superconducting in the past appear in all probability to require the presence of transition element impurities, in order to show the phenomenon. 相似文献
17.
R. O. Zaitsev 《JETP Letters》2010,92(1):46-51
The possibility of the existence of Cooper instability in transition-metal compounds has been established on the basis of
an idea about the strong interaction in a single unit cell. The phase diagram of the existence of the superconducting ordering
depending on the degree of underfilling (h
d
) of the 3d shells has been obtained. The nonphonon BCS constant has been calculated. 相似文献
18.
W. Dupont 《Solid State Communications》1981,39(3):525-529
The magnetic scattering of electrons is studied, paying special attention to the problem of coexistence of superconductivity and ferromagnetism. The utilized model consists of two electronic bands, one of which can become superconducting, and a system of localized spins. The calculated transition temperatures of the superconduction and the magnetic subsystems show regions of coexistence for not too large exchange interactions. Generally speaking, coexistence is favoured due to spin-orbit scattering as well as due to the interaction of the superconducting band with the normal band in certain cases. 相似文献
19.
20.
I. N. Khlyustikov 《Journal of Experimental and Theoretical Physics》2006,102(2):258-261
The critical supercooling field H sc is measured in aluminum single crystals and twinned bicrystals in a temperature range slightly below T c0 (T c0 ? 0.055 K < T < T c0), where T c0 is the critical superconducting transition temperature. It is found that, even in this small temperature range, the H sc(H c) dependence, which is considered to be identical to the H c3(H c) dependence for single crystals, is substantially nonlinear. The H sc(H c) dependences of the twinned bicrystals and single crystals are shown to be significantly different. The qualitative features of the phase diagram of the twinned aluminum bicrystals coincide with those of the phase diagram of twinning-plane superconductivity obtained earlier for tin in [1]. These findings allow the conclusion that the phenomenon of twinning-plane superconductivity also exists in face-centered cubic crystal lattices. 相似文献