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1.
A. Martín-Rodero 《物理学进展》2013,62(6):899-958
In this article, we review the state of the art on the transport properties of quantum dot systems connected to superconducting and normal electrodes. The review is mainly focused on the theoretical achievements, although a summary of the most relevant experimental results is also given. A large part of the discussion is devoted to the single-level Anderson-type models generalized to include superconductivity in the leads, which already contains most of the interesting physical phenomena. Particular attention is paid to the competition between pairing and Kondo correlations, the emergence of π-junction behavior, the interplay of Andreev and resonant tunneling, and the important role of Andreev bound states that characterized the spectral properties of most of these systems. We give technical details on the several different analytical and numerical methods which have been developed for describing these properties. We further discuss the recent theoretical efforts devoted to extend this analysis to more complex situations like multidot, multilevel or multiterminal configurations in which novel phenomena is expected to emerge. These include control of the localized spin states by a Josephson current and also the possibility of creating entangled electron pairs by means of non-local Andreev processes. 相似文献
2.
Z. P. Niu Z. M. Zheng D. Y. Xing 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(3):281-287
Four-component Bogoliubov-de Gennes equations are applied to study
tunneling conductance spectra of ferromagnet/ferromagnet/d-wave
superconductor (F1/F2/d-wave S) tunnel junctions and to find
out signs of spin-triplet pairing correlations induced in the
proximity structure. The pairing correlations with equal spins
arises from the novel Andreev reflection (AR), which requires at
least three factors: the usual AR at the F2/S interface, spin
flip in the F2 layer, and superconducting coherence kept up in
the F2 layer. Effects of angle α between magnetizations of
the two F layers, polarizations of the F1 and F2 layers, the
thickness of the F2 layer, and the orientation of the d-wave S crystal on the tunneling conductance are investigated. A conversion
from a zero-bias conductance dip at α = 0 to a zero-bias
conductance peak at a certain value of α can be seen as a
sign of generated spin-triplet correlations. 相似文献
3.
I. Shigeta Y. Tanaka F. Ichikawa Y. Asano 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(2):141-149
We propose a new approach of smearing origins of a zero-bias
conductance peak (ZBCP) in high-Tc superconductor tunnel
junctions through the analysis based on the circuit theory for a
d-wave pairing symmetry.
The circuit theory has been recently developed from conventional
superconductors to unconventional superconductors.
The ZBCP frequently appears in line shapes for this theory, in which the
total resistance was constructed by taking account of the effects
between a d-wave superconductor and a diffusive normal metal (DN) at a
junction interface, including the midgap Andreev resonant states (MARS),
the coherent Andreev reflection (CAR) and the proximity effect.
Therefore, we have analyzed experimental spectra with the ZBCP of
Ag-SiO-Bi2Sr2CaCu2O8+δ (Bi-2212) planar tunnel
junctions for the {110}-oriented direction by using a simplified
formula of the circuit theory for d-wave superconductors.
The fitting results reveal that the spectral features of the ZBCP are
well explained by the circuit theory not only excluding the Dynes's
broadening factor but also considering only the MARS and the DN
resistance.
Thus, the ZBCP behaviors are understood to be consistent with those of
recent studies on the circuit theory extended to the systems containing
d-wave superconductor tunnel junctions. 相似文献
4.
Z.-Y. Zhang 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(1):65-69
Along the lines of Blonder, Tinkham and Klapwijk, we investigate
the charge transport through ferromagnet/two-dimensional
electronic gas/d-wave superconductor (F/2DEG/S) junctions in the
presence of Rashba spin-orbit (SO) coupling and focus our
attention on the interplay between spin polarization and spin
precession. At zero spin polarization, the spin-mixing scattering
resulted from Rashba SO coupling decreases the zero-bias
conductance peak. Under spin polarization, spin precession
introduces novel Andreev reflection, which competes with the
effect of spin-mixing scattering. If the F layer is a half metal,
the later effect is overwhelmed by that of novel Andreev
reflection. As a result, the zero-bias conductance dip caused by
spin polarization is enhanced, and at strong Rashba SO coupling, a
split zero-bias peak is found in the gap. In an intermediate
region where the two effects are comparable with each other, the
zero-bias conductance shows a reentrant behavior as a function of
Rashba SO coupling. 相似文献
5.
Considering the Rashba spin-orbit interaction in the semiconductor, we study theoretically the spin-polarized transport in a two-dimensional ferromagnetic semiconductor double tunnel junctions by a quantum-mechanical approach. It is found that the transmission coefficient shows typical resonant transmission properties and the Rashba spin-orbit coupling has great different influences on the transmission coefficients of electrons with spin-up and down and tunnelling magnetoresistance (TMR). More importantly, the TMR is significantly enhanced by increasing the spin-orbit coupling, which is very useful for the designing of magnetic digital and memory sensor. 相似文献
6.
B. Frank K.Y. Platov W. Krech 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(2):187-192
The synchronization properties of a simple two-dimensional Josephson array consisting of two coupled SQUID cells are studied
within the Werthamer as well as the RCSJ model. Special emphasis is placed on the role of inductances arranged perpendicular
and parallel to the current bias direction for the phase locking behavior. The general behavior within the Werthamer model
is found to be similar to that within the RCSJ model. However, there are quantitative differences, e.g. an enhanced phase shift between the voltage oscillations within one cell and a shift of the parameter range for the in-phase
regime between different cells towards lower values of the McCumber parameter in the Werthamer model.
Received: 23 March 1998 / Revised: 3 June 1998 / Accepted: 9 June 1998 相似文献
7.
S. Piano J. W.A. Robinson G. Burnell M. G. Blamire 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(2):123-126
The physics of the π phase shift in ferromagnetic
Josephson junctions may enable a range of applications for
spin-electronic devices and quantum computing. We investigate
transitions from “0” to “π” states in Nb/Fe/Nb Josephson
junctions by varying the Fe barrier thickness from 0.5 nm to 5.5 nm. From magnetic measurements we estimate for Fe a magnetic
dead
layer of about 1.1 nm. By fitting the characteristic voltage
oscillations with existing theoretical models we extrapolate an
exchange energy of 256 meV, a Fermi velocity of 1.98 ×105
m/s and an electron mean free path of 6.2 nm, in agreement with
other reported values. From the temperature dependence of the
ICRN product we show that its decay rate exhibits a nonmonotonic
oscillatory behavior with the Fe barrier thickness. 相似文献
8.
C. Benjamin T. Jonckheere A. Zazunov T. Martin 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(3):279-289
We consider a model for a single molecule with a large frozen spin
sandwiched in between two BCS superconductors at equilibrium, and
show that this system has a π junction behavior at low
temperature. The π shift can be reversed by varying the other
parameters of the system, e.g., temperature or the position of the
quantum dot level, implying a controllable π junction with
novel application as a Josephson current switch. We show that the mechanism
leading to the π shift can be explained simply in terms of the contributions
of the Andreev bound states and of the continuum of states above the superconducting gap.
The free energy for certain configuration of parameters shows a
bistable nature, which is a necessary pre-condition for
achievement of a qubit. 相似文献
9.
V. N. Kushnir S. L. Prischepa C. Cirillo C. Attanasio 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(1):9-14
The influence of the finite transparency,
, of superconductor/normal metal
(S/N) interface on the critical temperature of proximity coupled layered
structures is investigated in the dirty limit on the basis of the
microscopic equations solved exactly by a matrix method. The calculated
theoretical curves satisfactory reproduce the experimental dependencies of
the critical temperature on the thickness of the superconducting layers in
N/S/N trilayers. The relation between the transparency coefficient and the
normal metal coherence length is also discussed. 相似文献
10.
O. Bourgeois P. Gandit J. Lesueur A. Sulpice X. Grison J. Chaussy 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(1):75-80
We report transport measurements on Superconductor/Ferromagnet/Superconductor (S/F/S) junctions: Nb/Al/Gd/Al/Nb where gadolinium
(Gd) is a weakly polarized ferromagnet. A sizeable critical current I
c is observed in the I(V) characteristics. This current can be modulated by a weak magnetic field, as expected for a Josephson current. With these
experiments, we establish that superconducting coherent transport survives across a small ferromagnetic layer. The penetration
depth of Cooper pairs in Gd has been measured. An extensive study of the Josephson critical current in temperature for different
thicknesses of magnetic compounds is presented. A comparison of transport measurements with S/N/S junction is given through
measurements made on Nb/Al/Y/Al/Nb, where yttrium (Y) is used as non magnetic rare earth metal.
Received 20 September 2000 and Received in final form 22 February 2001 相似文献
11.
Y. L. Feng K. Shen 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(1):105-110
We study chaos synchronization in two resistive-capacitive-inductive-shunted (RCL-shunted) Josephson junctions
(RCLSJJs) by using a common chaos driving. The numerical
simulations confirm that the synchronization of two RCLSJJs can be achieved
with a suitable driving intensity when the maximum condition Lyapunov
exponent (MCLE) is negative. 相似文献
12.
C. Hoffmann F. Lefloch M. Sanquer 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(4):629-633
We studied electronic relaxation in long diffusive superconductor/normal metal/superconductor (S/N/S) junctions by means of
current noise and transport measurements down to very low temperature (100mK). Samples with normal metal lengths of 4, 10
and 60μm have been investigated. In all samples the shot noise increases very rapidly with the voltage. This is interpreted
in terms of enhanced heating of the electron gas confined between the two S/N interfaces. Experimental results are analyzed
quantitatively taking into account electron-phonon interaction and heat transfer through the S/N interfaces. Transport measurements
reveal that in all samples the two S/N interfaces are connected incoherently, as shown by the reentrance of the resistance
at low temperature. The complementarity of noise and transport measurements allows us to show that the energy dependence of
the reentrance at low voltage is essentially due to the increasing effective temperature of the quasiparticles in the normal
metal.
Received 5 February 2002 / Received in final form 6 September 2002 Published online 31 October 2002
RID="a"
ID="a"e-mail: hoffmann@drfmc.ceng.cea.fr 相似文献
13.
R. De Luca A. Fedullo V. A. Gasanenko 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(4):461-467
The dynamical properties of symmetric quantum interferometers with equal
junctions of negligible capacitance have been studied by means of
perturbation analysis in the limit of small values of the parameter β. In
this limit, two characteristic time constants arise. These quantities may be
linked to two different dynamical processes in the system: the first is
related to the time evolution of the average superconducting phase
difference across the two junctions; the second defines the time scale for
flux motion. The response of the system to constant and time-dependent
externally applied magnetic fields is considered and a general perturbed
solution for the average superconducting phase difference and the fluxon
number variable is derived to first order in β. 相似文献
14.
R. De Luca A. Fedullo 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(1):59-66
The magnetic states of multi-junction superconducting quantum interference
device containing 2N identical conventional Josephson junctions are studied by
means of a perturbation analysis of the non-linear first-order ordinary
differential equations governing the dynamics of the Josephson junctions in
these devices. In the zero-voltage state, persistent currents are calculated
in terms of the externally applied magnetic flux Φex . The
resulting d.c. susceptibility curves show that paramagnetic and diamagnetic
states are present, depending on the value of Φex . The stability
of these states is qualitatively studied by means of the effective potential
notion for the system. 相似文献
15.
Sun Guoya Xing D.Y. Shen R. Lin H.Q. 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):33-38
The Nambu spinor Green's function approach is applied to calculating the density of states (DOS) and superconducting order
parameter in normal-metal/insulator/ferromagnet/superconductor (NM/I/FM/SC) junctions. It is found that the s-wave superconductivity and ferromagnetism can coexist near the FM/SC interface, which is induced by proximity effect. On
the SC side, the spin-dependent DOS appears both within and without the energy gap. On the FM side, the superconducting order
parameter displays a damped oscillation and the DOS exhibits some superconducting behavior. The calculated result for the
DOS in FM for “0 state” and “π state” can reproduce recent tunneling spectra in Al/Al2O3/PdNi/Nb tunnel junctions.
Received 1st July 2002 Published online 19 November 2002 相似文献
16.
Z.?Radovi? V.?Paltoglou N.?Lazarides N.?Flytzanis 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(2):229-236
We study the Josephson effect in ballistic double-barrier SINIS planar junctions, consisting of bulk superconductors (S),
a clean normal metal or semiconductor (N), and insulating interfaces (I) modeled as a δ-function potential-energy barriers.
We solve the scattering problem based on the Bogoliubov-de Gennes equations and derive a general expression for the dc Josephson
current, valid for arbitrary interfacial transparency, the Fermi wave vectors mismatch, and for different effective band masses.
The effect of transmission resonances on the Josephson current and on the normal conductance is analyzed for short junctions.
Curvature of the temperature dependence of the critical Josephson current is related to the presence of resonances at the
Fermi level and to the interfacial transparency. For thin semiconductor layers with negative effective masses of the carriers,
finite interfacial transparency and large Fermi wave vectors mismatch we find that an unusual and significant enhancement
of both the normal conductance and the critical Josephson current occurs at low temperatures due to the presence of an evanescent
mode localized at interfaces. 相似文献
17.
W. Ihra M. Leadbeater J.L. Vega K. Richter 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(3):425-435
We study the effect on the density of states in mesoscopic ballistic billiards to which a superconducting lead is attached.
The expression for the density of states is derived in the semiclassical S-matrix formalism shedding light onto the origin of the differences between the semiclassical theory and the corresponding
result derived from random matrix models. Applications to a square billiard geometry and billiards with boundary roughness
are discussed. The saturation of the quasiparticle excitation spectrum is related to the classical dynamics of the billiard.
The influence of weak magnetic fields on the proximity effect in rough Andreev billiards is discussed and an analytical formula
is derived. The semiclassical theory provides an interpretation for the suppression of the proximity effect in the presence
of magnetic fields as a coherence effect of time reversed trajectories. It is shown to be in good agreement with quantum mechanical
calculations.
Received 21 August 1999 and Received in final form 21 March 2001 相似文献
18.
S. Duhot R. Mélin 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(3):289-296
A Cooper pair from a s-wave superconductor (S) entering a conventional charge density wave (CDW) below the Peierls gap dephases
on the Fermi wavelength while one particle states are localized on the CDW coherence length ξCDW. It is thus practically impossible to observe a Josephson current through a CDW. The paths following different sequences
of impurities interfere destructively, due to the different electron and hole densities in the CDW. The same conclusion holds
for averaging over the conduction channels in the ballistic system. We apply two microscopic approaches to this phenomenon:
(i) a Blonder, Tinkham, Klapwijk (BTK) approach for a single highly transparent S-CDW interface; and (ii) the Hamiltonian
approach for the Josephson effect in a clean CDW and a CDW with non magnetic disorder. The Josephson effect through a spin
density wave (SDW) is limited by the coherence length ξSDW, not by the Fermi wave-length. A Josephson current through a SDW might be observed in a structure with contacts on a SDW
separated by a distance ξSDW. 相似文献
19.
H. Pan T. H. Lin 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(3):299-303
The supercurrent through an Aharonov-Bohm interferometer containing
two parallel quantum dots connected with two superconductor leads is
investigated theoretically. The possibility of controlling the
supercurrent is explored by tuning the quantum dot energy levels and
the total magnetic flux. By tuning the energy levels, both quantum
dots can be in the on-resonance or off-resonance states, and thus
the optimal modulation of the supercurrent can be achieved. The
supercurrent sign does not change by simply varying the quantum dot
energy levels. However, by tuning the magnetic flux, the
supercurrent can oscillate from positive to negative, which results
in the π-junction transition. 相似文献
20.
G. Bignon F. Pistolesi M. Houzet 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(3):465-474
We study theoretically the current-noise energy (voltage bias and temperature)
dependence for a N-N'-S structure, where N and S stand for bulk normal metal and
superconductor, respectively, and N' for a short diffusive normal
metal.
Using quasiclassical theory of current fluctuations we determine the
noise for arbitrary distributions of channel transparencies on both
junctions.
The differential Fano factor turns out to depend on both junction
transparencies and the ratio of the two conductances.
We discuss analytically the coherent and incoherent regimes and the
case when one of the two conductances dominates the other one.
Measurement of differential conductance and noise can be used to probe
the channel distribution of the interfaces.
We discuss recent experiments in the light of our results. 相似文献