Supercurrent tunneling between conventional and unconventional superconductors: A Ginzburg-Landau approach

Yip, Sungkit; Bonfim, O. F. de Alcantara; Kumar, Pradeep

doi:10.1103/physrevb.41.11214

Cited by 45 publications

(37 citation statements)

References 35 publications

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“…F 1 and F 2 are scalar under the operations of the complete symmetry of the system G including the crystal symmetry D 4h (or C 4v ), time reversal, spin rotation and gauge symmetry [84,75,76]. The interface term F 12 was chosen in the lowest order and so that it generates the correct boundary conditions [63,75,85,84]. Functions g 1 ( n 1 ) and g 2 ( n 2 ) should be invariant under all operations of the symmetry group of the respective half-space.…”

Section: B D-wave Picture Of a π-Junctionmentioning

confidence: 99%

Paramagnetic Meissner effect and related dynamical phenomena

2003

Physics Reports

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The hallmark of superconductivity is the diamagnetic response to external magnetic field. In striking contrast to this behavior, a paramagnetic response or paramagnetic Meissner effect was observed in ceramic high-Tc and in conventional superconductors. The present review is given on this interesting effect and related phenomena. We begin with a detailed discussion of experimental results on the paramagnetic Meissner effect in both granular and conventional superconductors. There are two main mechanisms leading to the paramagnetic response: the so called d-wave and the flux compression. In the first scenario, the Josephson critical current between two d-wave superconductors becomes negative or equivalently one has a π junction. The paramagnetic signal occurs due to the nonzero spontaneous supercurrent circulating in a loop consisting of odd number of π junctions. In addition to the d-wave mechanism we present the flux compression mechanism for the paramagnetic Meissner effect. The compression may be due to either an inhomogeneous superconducting transition or flux trap inside the giant vortex state. The flux trapping which acts like a total nonzero spontaneous magnetic moment causes the paramagnetic signal. The anisotropic pairing scenario is believed to be valid for granular materials while the flux trap one can be applied to both conventional and high-Tc superconductors. The study of different phenomena by a three-dimensional lattice model of randomly distributed π Josephson junctions with finite self-inductance occupies the main part of our review. By simulations one can show that the chiral glass phase in which chiralities are frozen in time and in space may occur in granular superconductors possessing d-wave pairing symmetry. Experimental attempts on the search for the chiral glass phase are analysed. Experiments on dynamical phenomena such as AC susceptibility, compensation effect, anomalous microwave absorption, aging effect, AC resistivity and enhancement of critical current by external electric fields are considered. These phenomena were studied by Monte Carlo and Langevin dynamics simulations which show satisfactory agreement with experiments. We present a resistively shunted junction model describing rich dynamics of Josephson junction networks.

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Section: B D-wave Picture Of a π-Junctionmentioning

confidence: 99%

Paramagnetic Meissner effect and related dynamical phenomena

2003

Physics Reports

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“…The free energy functional for Josephson junctions near T c results in the GL equations and the boundary conditions (BC) for them [20][21][22][23][24] . Consider symmetric junctions with a spatially constant width, which is much less than the Josephson penetration length, and with a plane interlayer at x = 0 of zero length within the GL approach.…”

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confidence: 99%

Anharmonic Josephson current in junctions with an interface pair breaking

Barash

2012

Phys. Rev. B

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Planar superconducting junctions with a large effective Josephson coupling constant and a pronounced interface pair breaking are shown to represent weak links with small critical currents and strongly anharmonic current-phase relations. The supercurrent near Tc is described taking into account the interface pair breaking as well as the current depairing and the Josephson coupling-induced pair breaking of arbitrary strengths. A new analytical expression for the anharmonic supercurrent, which is in excellent agreement with the numerical data presented, is obtained. In junctions with a large effective Josephson coupling constant and a pronounced interface pair breaking, the currentinduced depairing is substantially enhanced in the vicinity of the interface thus having a crucial influence on the current-phase relation despite a small depairing in the bulk. The Josephson current is one of the remarkable manifestations of quantum coherence on the macroscopic scale in condensed matter physics. The supercurrent depends on the phase difference of the order parameters across the junction interface. The study of the current-phase relation (CPR) in the junctions makes it possible to identify physical processes, which form supercurrents under diverse conditions. It is also beneficial for junction applications. The problem attracted much attention while studying both highly transparent junctions with strongly anharmonic CPRs and tunnel junctions, where the second harmonic of the supercurrent comes into play due to the suppression of the first one 1-10 . The latter takes place in the junctions involving unconventional superconductors with special interface-to-crystal orientations and at 0-π transitions.One of the earlier theoretical results, clarifying a variety of aspects of the problem, is the anharmonic CPR for the superconducting point contacts [11][12][13][14][15] . Due to the negligibly small current-induced pair breaking at any transparency value, the theory of point contacts is simplified. The depairing plays an important role in forming anharmonic CPRs in highly transparent planar junctions, unlike its negligible role in point contacts. Since the critical current j c of usual planar junctions becomes, with increasing transparency, comparable with the depairing current j dp in the bulk, the junctions do not represent weak links. In other words, in the junctions, the current-induced depairing brings about a pronounced anharmonicity only in the crossover from the tunnel Josephson current to the bulk superflow 1,16-18 .There are at least three types of pair breaking processes taking place in charge transport in the superconducting junctions: the pair breaking produced by the phase-dependent Josephson coupling, by the current and by the interface itself. These are the very same effects which can lead to a noticeably anharmonic CPR not only at low or intermediate temperatures, but also near T c . Here, I show that planar junctions with a large effective Josephson coupling constant and a pronounced interface pair breaking ca...

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“…The Josephson tunneling between conventional and unconventional superconductors are also studied by several authors, 23,24,13,25) but they assumed the unitary states for the triplet superconductors.…”

Section: )mentioning

confidence: 99%

“…Fenton 21) and Geshkenbein and Larkin 22) have shown that the Josephson effect between triplet and singlet superconductors can occur due to the spin-orbit coupling. The Josephson tunneling between conventional and unconventional superconductors are also studied by several authors, 23,24,13,25) but they assumed the unitary states for the triplet superconductors.…”

Section: )mentioning

confidence: 99%

Josephson Current between Triplet and Singlet Superconductors

Hasegawa

1998

J. Phys. Soc. Jpn.

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The Josephson effect between triplet and singlet superconductors is studied. Josephson current can flow between triplet and singlet superconductors due to the spin-orbit coupling in the spintriplet superconductor but it is finite only when triplet superconductor has Lz = −Sz = ±1, where Lz and Sz are the perpendicular components of orbital angular momentum and spin angular momentum of the triplet Cooper pairs, respectively. The recently observed temperature and orientational dependence of the critical current through a Josephson junction between UPt3 and Nb is investigated by considering a non-unitary triplet state.KEYWORDS: triplet superconductor, odd-parity, spin-orbit coupling Josephson junction Superconductivity in UPt 3 attracts a lot of interests. The existence of two different superconducting phases (A and B phases) as well as the third phase in the magnetic field (C phase) shows that the superconductivity in this system is not a conventional s-wave spin-singlet superconductivity. The possibility of the triplet superconductivity has been discussed.1, 2, 3, 4) The anisotropy of H c2 5) is discussed as an evidence for the triplet superconductivity with the d vector parallel to the c-axis. 2)Experimental results of the Knight shift observed by the NMR 6,7,8) and µSR 9) show the evidence for the triplet superconductivity in UPt 3 .10) The Knight shift is observed to be independent of temperature in the superconducting phase for H > 5 kOe.6, 7, 8) It decreases below T + c (A and B phases) for H < 5 kOe when H b and below T − c (B phase) for H < 2.3 kOe when H ĉ.8) The spin susceptibility for the spin-singlet superconductivity decreases as temperature becomes low, while that for the spin-triplet superconductivity is independent of temperature if the magnetic field is perpendicular to the d vector. Therefore, the magnetic-field and temperature dependences of the Knight sift of UPt 3 can be understood by the spin triplet states. The A and B phases are identified with respectively. 8, 11, 10) Since the Josephson effect is controlled by both the amplitude and the phase of the order parameters, it is a powerful tool to identify the symmetry of the order parameters. Recently, Sumiyama et al.12) have observed the Josephson critical current between a single crystal UPt 3 and an s-wave superconductor Nb. They also observed the Shapiro steps of thehω/(2e). If the Josephson current is caused by the higher-order tunneling or the proximity induced tunneling, the steps ofhω/(2ne) with n ≥ 2 should be observed. 13,14) Thus it is concluded that the Josephson current between UPt 3 and Nb is caused by the ordinary pair tunneling of the Cooper pairs. They found that the critical current is very small in the A phase and it increases steeply as temperature becomes lower than T The order parameters near the interface may be different from those in the bulk. Recently, it has been shown that the localized zero energy state exists at the interface when the order parameter change sign through the reflection.15) The zero energy stat...

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Supercurrent tunneling between conventional and unconventional superconductors: A Ginzburg-Landau approach

Cited by 45 publications

References 35 publications

Paramagnetic Meissner effect and related dynamical phenomena

Paramagnetic Meissner effect and related dynamical phenomena

Anharmonic Josephson current in junctions with an interface pair breaking

Josephson Current between Triplet and Singlet Superconductors

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