共查询到20条相似文献,搜索用时 31 毫秒
1.
Dong Zhengchao 《中国科学G辑(英文版)》2006,49(5):597-605
We study the Zeeman effect on the d-wave superconductor and tunneling spectrum in normal-metal(N)/d-wave superconductor(S) junction by applying a Zeeman magnetic field to the S. It is shown that: (1) the Zeeman magnetic field
can lead to the S gap decreasing, and with the increase in Zeeman energy, the superconducting state is changed to the normal
state, exhibiting a first-order phase transition; (2) the Zeeman magnetic field may make the zero-bias conductance peak split
into two peaks, and the energy difference between the two splitting peaks in the conductance spectrum is equal to 2h
0 (h
0 is the Zeeman energy); (3) both the barrier strength of interface scattering and the temperature can lower the magnitudes
of splitting peaks, of which the barrier strength can lead to the splitting peaks becoming sharp and the temperature can smear
out the peaks, however, neither of them can influence the Zeeman effect. 相似文献
2.
We solve a self-consistent equation for the d-wave superconducting gap and the effective exchange field in the mean-field approximation, study the Zeeman effects on the d-wave superconducting gap and thermodynamic potential. The Josephson currents in the d-wave superconductor (S)/insulating layer (I)/d-wave S junction are calculated as a function of the temperature, exchange field, and insulating barrier strength under a Zeeman magnetic field on the two d-wave Ss. It is found that the Josephson critical currents in d-wave S/d-wave S junction depend to a great extent on the relative orientation of the effective exchange field of the two S electrodes, and the crystal orientation of the d-wave S. The exchange field can under certain conditions enhance the Josephson critical current in a d-wave S/I/d-wave S junction. 相似文献
3.
Z.C. Dong 《Solid State Communications》2007,142(10):577-582
We solve a self-consistent equation for the d-wave superconducting gap and the magnetization in the mean-field approximation, study the Zeeman effects on the thermodynamic potential of d-wave superconductor (S) and coherent quantum transport in normal-metal (N)/d-wave S/N double tunnel junctions. Taking simultaneously into account the electron-injected current from one N electrode and the hole-injected current from the other N electrode, we derive a general formula for the differential conductance in a N/d-wave S/N system under a Zeeman magnetic field on the d-wave S. It is found that oscillations of all quasiparticle transport coefficients and differential conductance with the bias voltage and the thickness of the d-wave S depend to a great extent on the crystal orientation of the d-wave S. In the N/d-wave S/N junctions, the Zeeman magnetic field can lead to the Zeeman splitting of conductance peaks, and the temperature can reduce the coherent effect. 相似文献
4.
G. A. Ovsyannikov Yu. V. Kislinskii K. Y. Constantinian A. V. Shadrin V. V. Demidov A. M. Petrzhik 《Journal of Experimental and Theoretical Physics》2017,124(4):628-634
We have studied the current transport and magnetism in epitaxial hybrid superconducting mesa structures consisting of a cuprate superconductor and superconducting niobium with a manganite LaMnO3 (LMO) interlayer. We have shown experimentally using magnetic resonance that the magnetization, magnetic anisotropy parameters, and transition temperature to the ferromagnetic state of the interlayer of the structures are analogous to those of an autonomous LMO film grown on a neodymium gallate substrate. The estimate of the barrier height obtained from the dependence of the characteristic resistance of mesa structures on the interlayer thickness has shown the barrier height variation with the thickness in the range of 5–30 mV. The temperature dependences of the conductivity of the mesa structure in the range between superconducting transition temperatures of the superconductors can be described in the theory taking into account the d-wave nature of the superconductivity for one of the electrodes and the spin-filtering of carriers passing through the tunnel interlayer. Spin-filtering is confirmed by the tunnel magnetoresistance and the high sensitivity of mesa structures to a weak external magnetic field in a voltage interval smaller than the gap of niobium. 相似文献
5.
6.
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
7.
R. Gonczarek M. Krzyzosiak A. Gonczarek 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(3):299-308
In this paper we find and present on diagrams in the coordinates of η=2t1/t0 (the ratio of the second and the first nearest
neighbor hopping integrals) and n (the carrier concentration) the
areas of stability for the superconducting spin-singlet s-
and d-wave and the spin-triplet p-wave order
parameters hatching out during the phase transition from the normal
to the superconducting phase. The diagrams are obtained for an
anisotropic two-dimensional superconducting system with a relatively
wide partially-filled conduction band. We study a tight-binding
model with an attractive nearest neighbor interaction with the
amplitude V1, and the on-site interaction (with the amplitude
V0) taken either as repulsive or attractive. The problem of the
coexistence of the s-, p- and d-wave order
parameters is addressed and solved for chosen values of the ratio
V0/V1. A possible island of stability of the d-wave
order parameter in the s-wave order parameter environment for
a relatively strong on-site interaction is revealed. The triple
points, around which the s-, d-, and p-wave
order parameters coexist, are localized on diagrams. It is shown
that results of the calculations performed for the two-dimensional
tight-binding band model are dissimilar with some obtained within
the BCS-type approximation. 相似文献
8.
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
9.
A theoretical study of the fluctuation conductivity above Tc (paraconductivity) is reported for a d-wave superconductor with resonant scattering impurities. A d-wave system is modeled by tight-binding electrons in the two-dimensional squared lattice, and the impurity scattering is treated in the T-matrix approximation in a unitary limit. In calculating the Aslamazov–Larkin (AL) and the Maki–Thompson (MT) terms, we also consider effects of a short-wavelength cutoff in the fluctuation spectrum. The d-wave character in the AL and MT terms manifests itself to renormalization effects on the fluctuation amplitude and reduced temperature, whereas an anomalous-MT term is absent. The present calculations can describe fairly well experiments on the paraconductivity in zinc-doped cuprate superconductors provided that effects of a total-energy cutoff are taken into account. 相似文献
10.
Priyadarshini Kapri Saurabh Basu 《The European Physical Journal B - Condensed Matter and Complex Systems》2017,90(2):33
The tunneling conductance for a junction device consisting of a normal metal and a singlet superconductor is studied with Rashba spin orbit coupling (RSOC) being present in the metallic lead and the interface separating the two regions via an extended Blonder-Tinkham-Klapwijk (BTK) formalism. Interesting interplay between the RSOC and a number of parameters that have experimental significance, and characterize either the junction or the superconducting leads, such as the barrier transparency, quasiparticle lifetime, Fermi wavevector mismatch, an in-plane magnetic field and their effects on the tunneling conductance are investigated in details for both a s-wave and a d-wave superconductor. In an opaque barrier, in presence of a quasiparticle lifetime, a Fermi wavevector mismatch or an external in-plane magnetic field, RSOC enhances the conductance corresponding to low biasing energies, that is, at energies lesser than the superconducting gap, while the reverse is noted for energies exceeding the magnitude of the gap. Further, there are exciting anomalies noted in the conductance spectrum for the d-wave gap which can be understood by incorporating the interplay between the superconducting gap and the angle of incident of the charge carriers. 相似文献
11.
Taking into account the effects of quantum interference and interface scattering, combining the electron current with hole
current contribution to tunnel current, we study the coherent quantum transport in normal-metal/d-wave superconductor/ normal-metal (NM/d-wave SC/NM) double tunnel junctions by using extended Blonder-Tinkham-Klapwijk (BTK) approach. It is shown that all quasiparticle
transport coefficients and conductance spectrum exhibit oscillating behavior with the energy, in which periodic vanishing
of Andreev reflection (AR) above superconducting gap is found. In tunnel limit for the interface scattering strength taken
very large, there are a series of bound states of quasiparticles formed in SC. 相似文献
12.
Masaru Kato Tomio Koyama Masahiko Machida Masahiko Hayashi Hiromichi Ebisawa Takekazu Ishida 《Journal of Physics and Chemistry of Solids》2008,69(12):3286-3288
Using the Bogoliubov-de Gennes equation on the tight-binding electron model, we have investigated nano-structured anisotropic superconductors. For a π/4-rotated square d-wave superconducting plate, the superconducting symmetry becomes s+id, not only at the surfaces, but over the whole superconductor. Also we have investigated quasi-particle structures of this superconducting state. 相似文献
13.
14.
A. Ben Ali M. Héritier S. Charfi-Kaddour R. Bennaceur 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(1):53-61
A model of quasi-two-dimensional d-wave superconductor, with strong nesting properties of the Fermi surface is considered. The orbital effect of a moderate
magnetic field applied perpendicularly to the conducting planes is studied in the mean field approximation. It is shown that
the field can induce a time reversal symmetry breaking SDW order coexisting with the superconducting order and can open a
gap over the whole Fermi surface. The anomalies recently observed in the heat conductivity in might be ascribed to this effect.
Received 7 May 1999 and Received in final form 13 August 1999 相似文献
15.
Masaru Kato Yoshiteru Iwamoto Osamu Sato 《Physica C: Superconductivity and its Applications》2010,470(19):747-749
Using the de Gennes–Alexander equation, we have investigated the stable vortex structures in finite superconducting networks (10 × 10 holes) with disordered wires under an external magnetic field. Vortex structures change gradually with increasing magnetic field. For the network with a disordered wire at the edge, vortices are not pinned disordered hole, but enter into the network at the holes with the disorder. But for the network with two disordered wires, the vortex enters at the hole between two disordered wires. This behavior can be considered as the result of the nonlocality of superconductivity. 相似文献
16.
T. Watanabe H. Yokoyama M. Ogata 《Physica C: Superconductivity and its Applications》2009,469(15-20):1009-1012
To consider the origin of a pseudogap and a superconducting (SC) gap found in the high-Tc cuprates, we evaluated the momentum dependence of the singlet gap corresponding to the pseudogap and the SC gap in the t–J model, using an optimization variational Monte Carlo (VMC) method. In the underdoped regime, the singlet gap is significantly modified from the simple dx2-y2(d)-wave gap (∝ cos kx − cos ky) by the contribution of long-range pairings. Its angular dependence at the quasi Fermi surface is qualitatively consistent with those experimentally observed in both hole and electron-doped cuprates. On the other hand, a SC gap is almost unchanged, preserving the original simple d-wave form. Thus, it seems that the incoherent part of the singlet gap mainly influences the forms of observed gaps. 相似文献
17.
A time-reversal invariant topological superconductivity is suggested to be realized in a quasi-one-dimensional structure on a plane, which is fabricated by filling the superconducting materials into the periodic channel of dielectric matrices like zeolite and asbestos under high pressure. The topological superconducting phase sets up in the presence of large spin–orbit interactions when intra-wire s-wave and inter-wire d-wave pairings take place. Kramers pairs of Majorana bound states emerge at the edges of each wire. We analyze effects of the Zeeman magnetic field on Majorana zero-energy states. In-plane magnetic field was shown to make asymmetric the energy dispersion, nevertheless Majorana fermions survive due to protection of a particle–hole symmetry. Tunneling of Majorana quasiparticle from the end of one wire to the nearest-neighboring one yields edge fractional Josephson current with 4π-periodicity. 相似文献
18.
R. Gonczarek L. Jacak M. Krzyzosiak A. Gonczarek 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(2):171-186
Based upon the tight-binding formalism a model of a
high-Tc superconductor with isotropic and anisotropic
attractive interactions is considered analytically. Symmetry
facets of the group C4v are included within a method of
successive transformations of the reciprocal space. Complete sets
of basis functions of C4v irreducible representations are
given. Plausible spin-singlet and spin-triplet superconducting
states are classified with regard to the chosen basis functions. It
is displayed that pairing interaction coefficients and the
dispersion relation, which can be characterized by the parameter
η= 2t1/t0, have a diverse and mutually competing
influence on the value of the transition temperature. It is also
shown that
in the case of a nearly half-filled conduction band
and an anisotropic pairing interaction the spin-singlet
d-wave symmetry superconducting state is realized for
small values of the parameter η, whereas in the opposite
limit, for sufficiently large values, the spin-triplet
p-wave symmetry superconducting state has to be formed.
This result cannot be obtained within the Van Hove scenario or
BCS-type approaches, where the p-wave symmetry
superconducting state absolutely dominates. The specific heat jump
and the isotope shift as functions of the parameter η are
assessed and discussed for the d-wave symmetry singlet and
the p-wave symmetry triplet states. 相似文献
19.
Summary Using the Green's function method, the superconducting gap equation in the Anderson model with nearest-enighbour attraction
between correlated electrons is obtained. Thes- andp-wave solutions of this equation have been analysed for different choices of the parameters of the model.
In honour of Prof. Fausto Fumi on the occasion of his retirement from teaching. 相似文献
20.
Copper oxides become superconductors rapidly upon doping with electron holes, suggesting a fundamental pairing instability.
The Cooper mechanism explains normal superconductivity as an instability of a fermi-liquid state, but high-temperature superconductors
derive from a Mott-insulator normal state, not a fermi liquid. We show that precocity to pair condensation with doping is
a natural property of competing antiferromagnetism and d-wave superconductivity on a singly-occupied lattice, thus generalizing the Cooper instability to doped Mott insulators, with
significant implications for the high-temperature superconducting mechanism. 相似文献