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1.
A theory of the de Haas-van Alphen effect in type-II p-wave and D-wave superconductors (the latter corresponds to the B
1g
one-dimensional representation of group D
4h
) has been developed. Solutions for the order parameter and density of quasiparticle states near the upper critical field
have been calculated. If the curve enclosing the extremal cross section of the Fermi surface in the plane perpendicular to
the external magnetic field coincides with the line of nodes of the superconducting order parameter, the effect of the transition
to the superconducting state on the amplitude of magnetization oscillations is negligible. If the line of nodes is oriented
differently with respect to the applied magnetic field, the de Haas-van Alphen oscillations are suppressed in a manner qualitatively
similar to the case of conventional superconductors.
Zh. éksp. Teor. Fiz. 113, 2174–2192 (June 1998) 相似文献
2.
A microscopic theory of interplay of superconductivity and antiferromagnetism in rare earth ternary systems is developed from
first principles for less than half filledf atomic shells. Self consistent equations for the superconducting order parameter Δ and magnetic order parameter Γ, are derived
using a Green’s function technique and equation of motion method. The theory is applied to explain the experimental results
in the antiferromagnetic superconductor SmRh4B4. The present model explains true coexistence of superconductivity and antiferromagnetism and the suppression of superconductivity
by antiferromagnetism. The behaviour of superconducting order parameter (Δ), magnetic order parameter (Γ), the specific heat,
the density of states, free energy and critical field (H
c) is also studied for the system SmRh4B4. 相似文献
3.
The two-channel Anderson lattice model which has SU
(2) ⊗
SU
(2) symmetry is of relevance to understanding of the magnetic, quadrupolar and superconducting phases in U1-xThxBe13 or Pr based skutterudite compounds such as PrFe4P12 or PrOs4Sb12. Possible unconventional superconducting phases of the model are explored. They are characterized by a composite order parameter
comprising of a local magnetic or quadrupolar moment and a triplet conduction electron Cooper-pair. This binding of local
degrees of freedom removes the entropy of the non Fermi-liquid normal state. We find superconducting transitions in the intermediate
valence regime which are suppressed in the stable moment regime. The gap function is non analytic and odd in frequency: a
pseudo-gap develops in the conduction electron density of states which vanishes as |ω| close to ω = 0. In the strong intermediate valent regime, the gap function acquires an additional -dependence.
Received 28 February 2002 / Received in final form 18 April 2002 Published online 9 July 2002 相似文献
4.
We analyze the behavior of the density of states in a singlet s-wave superconductor with weak magnetic impurities in the clean limit. By using the method of optimal fluctuation and treating the order parameter self-consistently we show that the density of states is finite everywhere in the superconducting gap, and that it varies as ln(N(E) proportional to -/E-Delta(0)/((7-d)/4) near the mean field gap edge Delta(0) in a d-dimensional superconductor. In contrast to most studied cases the optimal fluctuation is strongly anisotropic. 相似文献
5.
V. A. Ivanov E. A. Ugolkova M. E. Zhuravlev 《Journal of Experimental and Theoretical Physics》1998,86(2):395-404
We have analyzed the electronic structure and superconducting properties of layered crystals based on BEDT-TTF salts (hereafter
denoted as ET), in which intramolecular interaction among electrons is important. For the case of realistic κ-packing of ET-molecules in a plane of ET2 dimers we have calculated the electron density of states. Using the calculated electronic structure, we have analyzed the
symmetry of the anisotropic superconducting pairing. The critical value of the effective attraction between electrons for
formation of a bound pair in an empty lattice has been estimated. The relation between the nodes of the d-type order parameter on the anisotropic Fermi surface and superconducting properties of the condensate is discussed in the
Bardeen-Cooper-Schrieffer (BCS) model. The results are in agreement with the known band parameters of the normal phase and
measurements of the magnetic field penetration depth, heat capacity as a function of temperature in the low-temperature range,
and NMR in κ-ET2X superconducting salts.
Zh. éksp. Teor. Fiz. 113, 715–733 (February 1998) 相似文献
6.
A. D. Semenov 《Journal of Experimental and Theoretical Physics》1999,89(3):552-558
This paper reports on an investigation of transient photoimpedance response to radiation, in other words, real-time variations
of the impedance induced by femtosecond optical pulses in superconducting films transferred to the mixed state by an external
magnetic field applied parallel to the c-axis. When the films were in a state characterized by the absence of dc resistivity, the response amplitude increased with the magnetic field faster than expected owing to the contribution of magnetic
vortices to the impedance of a superconductor with s-wave pairing of electrons. It turned out that the effect is due to a growth in the effective density of quasiparticle states
in the mixed state of a d-wave superconductor. In the absence of magnetic field, however, the response amplitude was higher at lower temperatures,
which contradicts the predictions of both models. Possible reasons for this feature in the response as a function of temperature
are discussed.
Zh. éksp. Teor. Fiz. 116, 1035–1047 (September 1999) 相似文献
7.
We present a theory of superconductivity in doped insulators. In the magnetic metal state of the compound we obtain the self-consistency
equations for the superconducting state in the spin-dependent impurity bands of both extended and localized states in the
initial insulator gap. A BCS-type triplet pairing field is considered. We show that the superconducting gap in which single-electron
extended states do not exist is overlapped by the distribution of the localized states. The formation of a latent superconducting
gap is discussed in connection with the unusual properties of high-T
c
compounds.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 5, 419–424 (10 March 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
8.
L. A. Openov 《JETP Letters》1997,66(10):661-667
The combined effect of nonmagnetic and magnetic defects and impurities on the critical temperatures of superconductors with
different anisotropies of the gap is studied theoretically within the weak coupling limit of the BCS model. An expression
is derived which relates the critical temperature to the relaxation rates of charge carriers on non-magnetic and magnetic
scatterers and to the coefficient of anisotropy of the superconducting order parameter on the Fermi surface. The particular
cases of d-wave, (s+d)-wave, and anisotropic s-wave superconductors are briefly discussed.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 10, 627–632 (25 November 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
9.
It is shown that in superconductors with anisotropic pairing the exponent of the power-law magnetic-field dependence of the
low-temperature heat capacity of the mixed state depends strongly on the multiplicities of the zeros of the superconducting
order parameter. As a result, an experimental determination of the corresponding power-law exponent makes it possible to judge
not only the presence of zeros in the order parameter but also the multiplicities of these zeros. An expression is obtained
for the spatially nonuniform quasiparticle density of states at low energies.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 5, 353–357 (10 March 1996) 相似文献
10.
The role of anisotropy of the coupling constant in the influence of nonmagnetic impurities on the behavior of the superconducting
transition temperature T
c is investigated in the high-temperature superconductor (HTSC) model, where high values of T
c result from an increase in the density of states near the Fermi surface. It is shown that this model is more sensitive to
impurities than the BCS model; Anderson compensation does not occur in the HTSC model, even for identical distributions of
the densities of states in the superconducting and impurity channels, and the impurity contributions are no longer linear
with respect to the impurity concentration in the vicinity of T
c. Anisotropy of the superconducting gap Δ and the possibility of its disappearance at certain points on the Fermi surface
due to various types of pairing are manifested in the stability of the superconducting phase against the influence of impurities.
Fiz. Tverd. Tela (St. Petersburg) 39, 1940–1942 (November 1997) 相似文献
11.
In the presence of zeros of the order parameter in an anisotropic superconductor, the combined effect of a magnetic field
and impurities leads to two different limiting magnetic-field dependences of the specific heat. These dependences are studied
both for Born scatterers and in the unitary limit for several specific examples of anisotropic pairing. A estimate is given
for the crossover field.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 8, 606–611 (25 April 1997) 相似文献
12.
H. Jirari R. Mélin N. Stefanakis 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(1):125-139
We consider the proximity effect in multiterminal ferromagnet/superconductor (FSF) hybrid structures in which two or three
electrodes are connected to a superconductor. We show that two competing effects take place in these systems: (i) pair breaking
effects due to the response to the exchange field induced in the superconductor; (ii) a reduction of the superconducting order
parameter at the interface that takes place already in NS junctions. We focus on this second effect that dominates if the
thickness of the S layer is small enough. We consider several single-channel electrodes connected to the same site. We calculate
the superconducting order parameter and the local density of state (LDOS). With two ferromagnetic electrodes connected to
a superconductor we find that the superconducting order parameter in the ferromagnetic alignment is larger than the superconducting
order parameter in the antiferromagnetic alignment ( > ), in agreement with [Eur. Phys. J. B 25, 373 (2002)]. If a third spin polarized electrode is connected to a superconductor we find that - can change sign as the transparency of the third electrode increases. This can be understood from the fact that the superconducting
order parameter is reduced if pair correlations among the ferromagnetic electrodes increase. If the two ferromagnetic electrodes
are within a finite distance we find Friedel oscillations in the Gorkov function but we still obtain > . 相似文献
13.
R. Allub 《Physica B: Condensed Matter》2011,406(9):1738-1743
We study the interplay between magnetic correlations of two Kondo impurities and superconducting singlet pairing. Performing a Schrieffer-Wolff transformation in the zero-bandwidth limit of the two-impurity Anderson model we obtain the Hamiltonian of two magnetic impurities and we add a superconducting term to the conduction electrons. The model allows us to study the effect of the magnetic correlation between the impurities on the superconducting ground state. At zero temperature, different superconducting ground states can be obtained depending on the magnitude of magnetic coupling between S1 and S2. For increasing coupling, the superconducting region is enlarged showing an interesting result: in the strong coupling limit, where the impurities are in a very strong ferromagnetic correlation state, half of the conduction electrons are decoupled from the local moments of the impurities and take advantage of the superconducting pairing lowering the ground state energy. On the contrary, when the coupling between S1and S2 decreases, the scenario of the two independent Kondo impurities in presence of superconductivity emerges and all the conduction electrons are involved in the pair breaking physics. At finite temperature, we obtain the phase diagram and we observe a region of parameters where the re-entrance phenomenon occurs. 相似文献
14.
P. Thalmeier 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(1):29-48
The Heavy Fermion state in UPd2Al3 may be approximately described by a dual model where two of the three U-5
f electrons are in a localized state split by the crystalline electric field into two low lying singlets with a splitting energy
Δ≃ 6 meV. The third 5
f electron has itinerant character and forms the Heavy Electron bands. Inelastic neutron scattering and tunneling experiments
suggest that magnetic excitons, the collective propagating crystal field excitations of the localized 5
f electrons, mediate superconducting (sc) pairing in UPd2Al3. A theory for this novel mechanism is developed within a nonretarded approach. A model for the magnetic exciton bands is
analyzed and compared with experiment. The sc pair potential which they mediate is derived and the gap equations are solved.
It is shown that this mechanism favors an odd parity state which is nondegenerate due to the combined symmetry breaking by
the crystalline electric field and the AF order parameter. A hybrid model including the spin fluctuation contribution to the
pairing is also discussed.
Received 22 October 2001 and Received in final form 28 February 2002 相似文献
15.
Yu. S. Barash A. G. Grishin M. Sigrist 《Journal of Experimental and Theoretical Physics》1997,85(1):168-172
The effect of the moment of a magnetic impurity on the order parameter of an unconventional superconductor is examined. The
coupling of the magnetic moment to the order parameter induces a locally time-reversal symmetry-breaking state which generates
a magnetic field distribution in the vicinity of the impurity. The magnetic field can cause precession of the magnetic moment.
The case of a spin polarized muon injected into the superconductor is discussed.
Zh. éksp. Teor. Fiz. 112, 304–312 (July 1997)
Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor. 相似文献
16.
The phase diagram of a layered superconductor in a large parallel magnetic field is calculated. This includes a calculation of the lower critical field beyond which the superconductor is in the FFLO-state and possesses a spatially modulated order parameter and spin polarization. The order parameter, spin polarization, free-energy density, and phase boundaries of this unconventional superconducting phase are evaluated numerically in the complete B–T plane. The analysis suggests that the transition at the lower critical field is of second order, and not of first order, as previously assumed. The order parameter of the FFLO-state merges continuously into the uniform superconducting state. 相似文献
17.
Poli N Morten JP Urech M Brataas A Haviland DB Korenivski V 《Physical review letters》2008,100(13):136601
We study spin transport in a superconducting nanowire using a set of closely spaced magnetic tunnel contacts. We observe a giant enhancement of the spin accumulation of up to 5 orders of magnitude on transition into the superconducting state, consistent with the expected changes in the density of states. The spin relaxation length decreases by an order of magnitude from its value in the normal state. These measurements, combined with our theoretical model, allow us to distinguish the individual spin-flip mechanisms present in the transport channel. Our conclusion is that magnetic impurities rather than spin-orbit coupling dominate spin-flip scattering in the superconducting state. 相似文献
18.
19.
É. Z. Kuchinskii 《Physics of the Solid State》2003,45(6):1017-1025
A simple, exactly solvable model of a pseudogap state induced by fluctuations of dielectric short-range order is used to study the peculiarities of the electronic spectral density and density of states of a superconductor in the model of the Fermi surface with hot patches. The problem is considered for arbitrary values of the short-range order correlation length ξcorr. It is shown that the absence of self-averaging of the superconducting order parameter over the random field of dielectric fluctuations causes the spectral density and density of states to change significantly. The superconducting character of these quantities persists in a wide temperature range above the temperature T c of the superconducting transition, which is uniform over the whole sample. 相似文献