Josephson junction through a disordered topological insulator with helical magnetization

Zyuzin, A. A.; Alidoust, Mohammad; Loss, Daniel

doi:10.1103/physrevb.93.214502

Cited by 95 publications

(122 citation statements)

References 41 publications

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“…Results presented here imply that the breaking of the underlying symmetries can be achieved in superconductorquantum dot structures while maintaining coherent transport of Cooper pairs. In this context, our experiment is directly related to the efforts of studying triplet superconductivity and superconducting spintronics 26 as well as in achieving topological superconducting phase in quantum dots coupled to an s-wave superconductor 16,[27][28][29][30][31][32] . Aside from that, a gate-tunable phase offset may open novel possibilities for the realization of electrically controlled flux-and phase-based quantum bits 33 , superconducting computer memory components 34 , as well as superconducting 'phase' batteries and rectifiers 4,35 .…”

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confidence: 99%

Josephson ϕ0-junction in nanowire quantum dots

et al. 2016

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The Josephson e ect describes supercurrent flowing through a junction connecting two superconducting leads by a thin barrier 1 . This current is driven by a superconducting phase di erence ϕ between the leads. In the presence of chiral and time-reversal symmetry of the Cooper pair tunnelling process 2 , the current is strictly zero when ϕ vanishes. Only if these underlying symmetries are broken can the supercurrent for ϕ = 0 be finite [3][4][5] . This corresponds to a ground state of the junction being o set by a phase ϕ 0 , di erent from 0 or π. Here, we report such a Josephson ϕ 0 -junction based on a nanowire quantum dot. We use a quantum interferometer device to investigate phase o sets and demonstrate that ϕ 0 can be controlled by electrostatic gating. Our results may have far-reaching implications for superconducting flux-and phase-defined quantum bits as well as for exploring topological superconductivity in quantum dot systems.The process of Cooper pair tunnelling through a Josephson junction (JJ) is, in general, symmetric with respect to time inversion. This has a profound consequence for the JJ current-phase relation, I (ϕ). In particular it imposes the condition I (−ϕ) = −I (ϕ), which in turn results in I (ϕ = 0) being strictly zero. The I (ϕ = 0) = 0 condition is a consequence of the fact that for each process contributing to current flowing in one direction there is an opposite time-reversed process, in which spin-up and spin-down electrons are reversed, that exactly cancels this current. However, time inversion is not the only symmetry which can protect the I (ϕ = 0) = 0 condition. For example, in JJs based on single-domain ferromagnets, time inversion is broken, but the supercurrent is still zero for ϕ = 0 owing to chiral symmetry-that is, the symmetry between leftward and rightward tunnelling. This symmetry ensures that the tunnelling coefficient describing the electron tunnelling from the left lead to the right lead is exactly the same as the one describing the tunnelling in reverse, from the right lead to the left lead. The two tunnelling processes (leftward and rightward) cancel each other, which again results in I (ϕ = 0) being strictly zero. This is even the case for so-called π-junctions 6 , in which the current flow is reversed compared to usual JJs, but still the underlying symmetries guarantee zero current for ϕ = 0. To create conditions for a non-zero supercurrent to flow at ϕ = 0, both symmetries need to be broken 7 . Various ways have been proposed theoretically to break the underlying symmetries and create ϕ 0 -junctions, including ones based on non-centrosymmetric or multilayer ferromagnets 3,8 , quantum point contacts 4 , topological insulators 9,10 , diffusive systems 11,12 , nanowires 13,14 and quantum dots 5,15,16 . Alternatively, an effective built-in phase offset can be obtained by combining 0-and π-junctions in parallel 17,18 . However, no experimental demonstration of a ϕ 0 -junction has been reported until now.In quantum dots (QDs), breaking of both symmetries can be achiev...

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confidence: 99%

Josephson ϕ0-junction in nanowire quantum dots

et al. 2016

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“…Hence, we now proceed to apply our formulated quasiclassical model to hybrid structures made of disordered Weyl semimetals and superconductors, which are practical platforms that the Eilenberger and Usadel equations are able to describe them properly. We note that the quasiclassical Eilenbeger and Usadel approaches were also generalized for spin-orbit coupled systems [70][71][72][73][74][75] , surface channels of topological insulators [63][64][65] , and black phosphorus monolayer (phosphorene) 27 in the presence of superconductivity and a Zeeman field. A specific configuration is depicted in Fig.…”

Section: Eilenberger and Usadel Equationsmentioning

confidence: 98%

Self-biased current, magnetic interference response, and superconducting vortices in tilted Weyl semimetals with disorder

Alidoust

2018

Phys. Rev. B

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We have generalized a quasiclassical model for Weyl semimetals with a tilted band in the presence of an externally applied magnetic field. This model is applicable to ballistic, moderately disordered, and samples containing a high density of nonmagnetic impurities. We employ this formalism and show that a self-biased supercurrent, creating a ϕ 0 -junction, can flow through a triplet channel in Weyl semimetals. Furthermore, our results demonstrate that multiple supercurrent reversals are accessible through varying junction thickness and parameters characterizing Weyl semimetals. We discuss the influence of different parameters on the Fraunhofer response of charge supercurrent, and how these parameters are capable of shifting the locations of proximityinduced vortices in the triplet channel. arXiv:1811.11765v2 [cond-mat.mes-hall]

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“…This is the so called ϕ 0 -junction, and its interpretation in terms of the inverse magneto-electric effect was reported in 46 . It was actively studied recently in half-metal junctions, noncoplanar ferromagnetic junctions, ferromagnetic Josephson junctions with spin orbit interaction or TI surface states [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] .…”

Section: Introductionmentioning

confidence: 99%

Quasiclassical theory of magnetoelectric effects in superconducting heterostructures in the presence of spin-orbit coupling

Bobkova

Bobkov

2017

Phys. Rev. B

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The quasiclassical theory in terms of equations for the Green's functions (Eilenberger equations) is generalized in order to allow for quantitative description of the magneto-electric effects and proximity-induced triplet correlations in the presence of spin-orbit coupling in hybrid superconducting systems. The formalism is valid under the condition that the spin-orbit coupling is weak with respect to the Fermi energy, but exceeds the superconducting energy scale considerably. On the basis of the derived formalism it is shown that the triplet correlations in the spin-orbit coupled normal metal can be induced by proximity to a singlet superconductor without any exchange or external magnetic field. They contain an odd-frequency even-momentum component, which is stable against disorder. The value of the proximity-induced triplet correlations is of the order of ∆so/εF , that is absent in the framework of the standard quasiclassical approximation, but can be described by our theory. The spin polarization, induced by the Josephson current flowing through the superconductor/Rashba metal/superconductor junction, is also calculated.

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Josephson junction through a disordered topological insulator with helical magnetization

Cited by 95 publications

References 41 publications

Josephson ϕ0-junction in nanowire quantum dots

Josephson ϕ0-junction in nanowire quantum dots

Self-biased current, magnetic interference response, and superconducting vortices in tilted Weyl semimetals with disorder

Quasiclassical theory of magnetoelectric effects in superconducting heterostructures in the presence of spin-orbit coupling

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