A superconductor-semiconducting nanowire-superconductor heterostructure in the presence of spin-orbit coupling and magnetic field can support a supercurrent even in the absence of phase difference between the superconducting electrodes. We investigate this phenomenon—the anomalous Josephson effect—employing a model capable of describing many bands in the normal region. We discuss the geometrical and symmetry conditions required to have a finite anomalous supercurrent, and in particular we show that this phenomenon is enhanced when the Fermi level is located close to a band opening in the normal region.
We present a study of an Hanbury Brown and Twiss (HBT) interferometer realized with anyons. Such a device can directly probe entanglement and fractional statistics of initially uncorrelated particles. We calculate HBT cross-correlations of Abelian Laughlin anyons. The correlations we calculate exhibit partial bunching similar to bosons, indicating a substantial statistical transmutation from the underlying electronic degrees of freedom. We also find qualitative differences between the anyonic signal and the corresponding bosonic or fermionic signals, indicating that anyons cannot be simply thought as intermediate between bosons and fermions.Two-particle interference is a major pillar of quantum mechanics, very much like the phenomenon of single particle interference. Such interference has been observed with photons in the historical Hanbury Brown and Twiss (HBT) experiment [1,2], and much later with electrons [3]. Quantum Hall systems can exhibit emergent particles (dubbed anyons) with fractional statistics [4,5]. Despite intensive study, direct signatures of anyonic statistics remain elusive. Here we study an HBT interferometer with anyons, which can directly probe entanglement and fractional statistics of initially uncorrelated particles. Specifically, we calculate HBT crosscorrelations of Abelian Laughlin anyons. The correlations exhibit partial bunching similar to bosons, indicating a substantial statistical transmutation from the underlying electronic degrees of freedom [6]. Furthermore, we find qualitative differences between the anyonic signal and the corresponding bosonic or fermionic signals, indicating that anyons cannot be simply thought as intermediate between bosons and fermions.Edge channels of a fractional quantum Hall system offer a natural framework to study transport properties of anyons. Earlier attempts to consider entanglement of such quasiparticles (QPs) either addressed time-resolved correlation functions [7] (which may be very hard to measure) or relied on a single source geometry setup [8][9][10] (which may introduce superfluous interaction-induced correlations). Here we study zero frequency currentcurrent correlations in a truly HBT interferometer setup, whose physics is governed by QPs dynamics. Because of their fractional charge and fractional statistics, scattering of these QPs results in non trivial correlations. Below, we consider the case ν = 1/3 for concreteness, but, our analysis can be generalized to other Laughlin fractions.Consider first a heuristic estimate of these correlations, outlined in Fig. 1. Two particles are emitted respectively from two sources S 1 and S 2 and scattered towards two detectors D 1 and D 2 by a beam splitter, e.g. a quantum point contact (QPC) for electrons and QPs, or a half silvered mirror for photons. We evaluate the probability P (m, 2 − m), m = 0, 1, 2, that m particles are collected at the drain D 1 while (2 − m) are collected at the drain D 2 . Consider, e.g., the diagrams contributing to P (1, 1) [cf. Fig. 1(a)]. Each diagram represents an amp...
The study of superconductor/ferromagnet interfaces has generated a great interest in the last decades, leading to the observation of equal spin spin triplet supercurrent and 0 − π transitions in Josephson junctions where two superconductors are separated by an itinerant ferromagnet. Recently, spin-filter Josephson junctions with ferromagnetic barriers have shown unique transport properties, when compared to standard metallic ferromagnetic junctions, due to the intrinsically non-dissipative nature of the tunneling process. Here we present the first extensive characterization of spin polarized Josephson junctions down to 0.3 K, and the first evidence of an incomplete 0 − π transition in highly spin polarized tunnel ferromagnetic junctions. Experimental data are consistent with a progressive enhancement of the magnetic activity with the increase of the barrier thickness, as neatly captured by the simplest theoretical approach including a non uniform exchange field. For very long junctions, unconventional magnetic activity of the barrier points to the presence of spin-triplet correlations.The interaction of superconductors with materials other than simple insulators or metals has made accessible a series of conceptually new challenges. Of particular interest to this work, Josephson junctions (JJs) with ferromagnetic materials separating two superconductors have been extensively characterized over the last decade. The simultaneous presence of the macroscopic phase coherence of superconductors and the exchange interaction of ferromagnetic materials is indeed of great value in the study of fundamental questions on possible pairing states in superconductors [1,2], demonstrating the presence of spin-polarized triplet supercurrents [3][4][5][6][7][8][9], and for potential applications in a wide range of cutting edge areas, such as spintronics [10,11], memory applications for high performance computing [12][13][14][15][16][17][18] and circuit components such as π shifters and phase qubits [19][20][21][22][23]. A playground where different forms of order can cooperate and interfere is of considerable value for inspiring other fields of physics [1,2].The existing literature focuses mostly on metallic superconductor/ferromagnet/superconductor (SFS) junctions, where the evidence of long-range spin triplet correlations is well established [3][4][5][6][7][8]: in the presence of equalspin Cooper pairs, the magnitude of the critical current I C decays much more slowly with magnetic barrier thickness than expected for standard singlet supercurrents [4,5]. In fact, spin-polarized Cooper pairs can survive at much longer length scales when compared to opposite spin Cooper pairs, and are practically immune to depairing induced by the presence of an exchange field [1,2]. Such junctions, together with superconducting spin valve devices, are likely to be the building blocks for future spintronic devices [11]. While metallic SFS junctions have been extensively characterized, the physics of ferromagnetic junctions with insulating barriers, l...
We develop a finite-element technique that allows one to evaluate correction of the order of G Q to various transport characteristics of arbitrary nanostructures. Common examples of such corrections are the weaklocalization effect on conductance and universal conductance fluctuations. Our approach, however, is not restricted to conductance only. It allows one in the same manner to evaluate corrections to the noise characteristics, superconducting properties, strongly nonequilibrium transport, and transmission distribution. To enable such functionality, we consider Green's functions of arbitrary matrix structure. We derive a finite-element technique from Cooperon and diffuson ladders for these Green's functions. The derivation is supplemented with application examples. Those include transitions between ensembles and the Aharonov-Bohm effect.
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