Josephson response of a conventional and a noncentrosymmetric superconductor coupled via a double quantum dot

Sothmann, Björn; Tiwari, Rakesh P.

doi:10.1103/physrevb.92.014504

Cited by 15 publications

(9 citation statements)

References 57 publications

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“…3(a). This is reminiscent of the φ-junction behavior of the Josephson current in certain Josephson junctions with singlet and triplet pairing [31][32][33][34][35][36][37][38][39][40]. We remark that the φ-junction behavior of the thermal conductance here is due to the wave vector difference between electrons and holes and, thus, of a completely different origin than the φ-junction behavior of the Josephson current in the aforementioned junctions.…”

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confidence: 59%

Fingerprint of topological Andreev bound states in phase-dependent heat transport

Sothmann

Hankiewicz

2016

Phys. Rev. B

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We demonstrate that phase-dependent heat currents through superconductor-topological insulator Josephson junctions provide a useful tool to probe the existence of topological Andreev bound states, even for multi-channel surface states. We predict that in the tunneling regime topological Andreev bound states lead to a minimum of the thermal conductance for a phase difference φ = π, in clear contrast to a maximum of the thermal conductance at φ = π that occurs for trivial Andreev bound states in superconductor-normal metal tunnel junctions. This opens up the possibility that phasedependent heat transport can distinguish between topologically trivial and nontrivial 4π modes. Furthermore, we propose a superconducting quantum interference device geometry where phasedependent heat currents can be measured using available experimental technology.Introduction.-At the interface between a normal metal and a superconductor, an electron with an energy inside the superconducting gap gets reflected from the superconductor as a hole in a process called Andreev reflection [1]. In a superconductor-normal metalsuperconductor (S-N-S) junction, this electron-hole conversion leads to the formation of Andreev bound states with discrete energies [2]. In the case of a short, onedimensional junction there is exactly one pair of such bound states with energy ε = ±∆ 1 − D sin 2 φ/2 where D denotes the transmission probability of the junction in the normal state, ∆ is the absolute value of the superconducting pair potential and φ the phase difference across the junction [3].Recently, there has been a growing interest in Josephson junctions based on topological insulators (TIs). The surface states of a three-dimensional TI give rise to the formation of topologically nontrivial helical Andreev bound states with energy ε = ±∆ cos φ/2 [4], i.e., they exhibit a zero-energy crossing at φ = π. In contrast to the S-N-S case where even weak backscattering leads to a splitting of the accidental degeneracy of Andreev bound states at φ = π, the crossing in the S-TI-S case is robust due to topological protection. It gives rise to a 4π-periodic Josephson current [5]. The latter is difficult to observe in experiment [6,7] as it is a single-channel effect and subject to quasiparticle poisoning. Although recent experiments provide some evidence for the existence of helical Andreev bound states in the non-sinusoidal current phase relation [8], in the diffraction pattern [9] and missing Shapiro steps in the ac Josephson effect [10], it is still an outstanding challenge to distinguish between topologically trivial and nontrivial 4π modes.Interestingly, not only the Josephson current but also the heat current between two superconductors kept at different temperatures depends on the phase difference across the junction. The effect arises due to the interference between quasiparticles carrying heat and Cooper pairs carrying phase information. It was theoretically Since heat currents are carried by quasiparticles with energies above or below the superconducting g...

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confidence: 59%

Fingerprint of topological Andreev bound states in phase-dependent heat transport

Sothmann

Hankiewicz

2016

Phys. Rev. B

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“…The phase difference between the two Majorana wires will drive finite Josephson current through them, which can be directly evaluated by the following formula 37 …”

Section: Modelmentioning

confidence: 99%

Influence of an embedded quantum dot on the Josephson effect in the topological superconducting junction with Majorana doublets

Gong

Gao

Shan

et al. 2016

Sci Rep

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One Majorana doublet can be realized at each end of the time-reversal-invariant Majorana nanowires. We investigate the Josephson effect in the Majorana-doublet-presented junction modified by different inter-doublet coupling manners. It is found that when the Majorana doublets couple indirectly via a non-magnetic quantum dot, only the normal Josephson effect occurs, and the fermion parity in the system just affects the current direction and amplitude. However, one magnetic field applied on the dot can induce the fractional Josephson effect in the odd-parity case. Next if the direct and indirect couplings between the Majorana doublets coexist, no fractional Josephson effect takes place, regardless of the presence of magnetic field. Instead, there almost appears the π-period-like current in some special cases. All the results are clarified by analyzing the influence of the fermion occupation in the quantum dot on the parity conservation in the whole system. We ascertain that this work will be helpful for describing the dot-assisted Josephson effect between the Majorana doublets.

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“…Several previous works on similar systems completely neglect the possibility of EC processes [7,52–54 71–72]. In other works EC coupling is taken into account [44,61,64–65 67–68 73], but in most of the cases it is defined as a constant coupling term that is equivalent to the IT coupling used here, therefore they can be incorporated to the same term.…”

Section: Introductionmentioning

confidence: 99%

Transport signatures of an Andreev molecule in a quantum dot–superconductor–quantum dot setup

Scherübl¹,

Pályi²,

Csonka³

2019

Beilstein J. Nanotechnol.

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Hybrid devices combining quantum dots with superconductors are important building blocks of conventional and topological quantum-information experiments. A requirement for the success of such experiments is to understand the various tunneling-induced non-local interaction mechanisms that are present in the devices, namely crossed Andreev reflection, elastic co-tunneling, and direct interdot tunneling. Here, we provide a theoretical study of a simple device that consists of two quantum dots and a superconductor tunnel-coupled to the dots, often called a Cooper-pair splitter. We study the three special cases where one of the three non-local mechanisms dominates, and calculate measurable ground-state properties, as well as the zero-bias and finite-bias differential conductance characterizing electron transport through this device. We describe how each non-local mechanism controls the measurable quantities, and thereby find experimental fingerprints that allow one to identify and quantify the dominant non-local mechanism using experimental data. Finally, we study the triplet blockade effect and the associated negative differential conductance in the Cooper-pair splitter, and show that they can arise regardless of the nature of the dominant non-local coupling mechanism. Our results should facilitate the characterization of hybrid devices, and their optimization for various quantum-information-related experiments and applications.

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Josephson response of a conventional and a noncentrosymmetric superconductor coupled via a double quantum dot

Cited by 15 publications

References 57 publications

Fingerprint of topological Andreev bound states in phase-dependent heat transport

Fingerprint of topological Andreev bound states in phase-dependent heat transport

Influence of an embedded quantum dot on the Josephson effect in the topological superconducting junction with Majorana doublets

Transport signatures of an Andreev molecule in a quantum dot–superconductor–quantum dot setup

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