Gapless Andreev bound states in the quantum spin Hall insulator HgTe

Bocquillon, Erwann; Deacon, Russell; Wiedenmann, Jonas; Leubner, Philipp; Klapwijk, T. M.; Brüne, C.; Ishibashi, Koji; Buhmann, H.; Molenkamp, Laurens W.

doi:10.1038/nnano.2016.159

Cited by 316 publications

(355 citation statements)

References 41 publications

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“…The simplest realization of a non-abelian anyon are Majorana bound states (MBSs) in topological superconductors (TSs) [3]. It has been proposed that such a TS can be induced by an s-wave superconductor (SC) in systems of nanowires with spinorbit interaction (SOI) subject to a Zeeman field [4][5][6][7], in chains of magnetic atoms [8][9][10][11] and in topological insulators [12][13][14][15][16][17]. However, providing experimental evidence for the existence of this new phase of matter has remained a major challenge.…”

mentioning

confidence: 99%

Detecting topological superconductivity with φ0 Josephson junctions

2017

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The interplay of superconductivity, magnetic fields, and spin-orbit interaction lies at the heart of topological superconductivity. Remarkably, the recent experimental discovery of ϕ0 Josephson junctions by Szombati et al. [1], characterized by a finite phase offset in the supercurrent, require the same ingredients as topological superconductors, which suggests a profound connection between these two distinct phenomena. Here, we theoretically show that a quantum dot ϕ0 Josephson junction can serve as a new qualitative indicator for topological superconductivity: Microscopically, we find that the phase shift in a junction of s−wave superconductors is due to the spin-orbit induced mixing of singly occupied states on the qantum dot, while for a topological superconductor junction it is due to singlet-triplet mixing. Because of this important difference, when the spin-orbit vector of the quantum dot and the external Zeeman field are orthogonal, the s-wave superconductors form a π Josephson junction while the topological superconductors have a finite offset ϕ0 by which topological superconductivity can be distinguished from conventional superconductivity. Our prediction can be immediately tested in nanowire systems currently used for Majorana fermion experiments and thus offers a new and realistic approach for detecting topological bound states. Non-abelian anyons are the building blocks of topological quantum computers [2]. The simplest realization of a non-abelian anyon are Majorana bound states (MBSs) in topological superconductors (TSs) [3]. It has been proposed that such a TS can be induced by an s-wave superconductor (SC) in systems of nanowires with spinorbit interaction (SOI) subject to a Zeeman field [4][5][6][7], in chains of magnetic atoms [8][9][10][11] and in topological insulators [12][13][14][15][16][17]. However, providing experimental evidence for the existence of this new phase of matter has remained a major challenge.Here we present a new qualitative indicator of MBS based on ϕ 0 Josephson junctions (ϕ 0 JJs). In ϕ 0 JJs the Josephson current is offset by a finite phase, ϕ 0 , so that a finite supercurrent flows even when the phase difference between the superconducting leads and the magnetic flux enclosed by the Josephson junction (JJ) vanishes. Such ϕ 0 JJs have been discussed in systems based on unconventional superconductors [18][19][20][21][22] [32,33]. Recently, the connection between ϕ 0 JJs based on nanowires and TSs has also been discussed [34]. Most relevant for the present work, the emergence of a ϕ 0 JJ was theoretically predicted [35][36][37] in a system of a quantum dot (QD) with SOI subject to a Zeeman field when coupled to s-wave superconducting leads and observed in recent experiments [1]. Interestingly, the ingredients for observing a ϕ 0 JJ in this type of system largely overlap with those required to generate MBSs. In this work, we focus on two models for ϕ 0 JJs based on QDs which, compared to previous studies [35][36][37], are in the singlet-triplet anticrossing regime. In the...

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confidence: 99%

Detecting topological superconductivity with φ0 Josephson junctions

2017

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“…Two MQPs together can favor the 2f 0 Josephson current 51 . Recent experiment with superconductor-TI-superconductor system also found an enhanced 2f 0 in the nontrivial region 27 , while the signal of 2f 0 is small when the system lies in the trivial region. Our numerical results are consistent with the experiment.…”

Section: Iii2 Comparison Of the Josephson Current For Different Regmentioning

confidence: 94%

“…Since the 4π Josephson effect is a unique transport property of MQPs, a lot of research has been dedicated towards its realization. Several groups have attempted to build a superconductor-topological * jieliuphy@xjtu.edu.cn insulator-superconductor junction which is also expected to present the 4π Josephson current [23][24][25][26][27][28] . Indeed, Molenkamp's group has showed the signal of 4π-periodic Josephson Effect in such a junction [26][27][28] .…”

Section: Introductionmentioning

confidence: 99%

Quench dynamics of the Josephson current in a topological Josephson junction

Sun

Liu

2018

Phys. Rev. B

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The 4π-periodic Josephson Effect is a distinguishing feature of a topological Josephson junction. However, stringent conditions make it hard to observe in experiments. In this work, we study the transient transport properties in a topological Josephson junction numerically. We show that the 4π Josephson current can be sustained under nonequilibrium conditions. The properties of the Josephson current are analyzed for different conditions, and three main regimes are identified: First, when both the superconducting wires of the Josephson junction lie in the topologically nontrivial region, a 4π Josephson current can appear upon suddenly applying a DC voltage. Second, when one superconducting wire lies in the trivial region, while the other wire lies in the non-trivial region, the Josephson current is 2π periodic but the component of the higher order Josephson current increases. Third, when both wires lie in the trivial region, a stable 2π Josephson current is observed. Most importantly, the fractional Josephson Effect is fragile in the presence of disorder. Hence, experiments should be designed carefully to eliminate the effect of disorder. These results could be helpful to optimize fine-tuning of the experimental parameters to observe the 4π-periodic Josephson current in a topological Josephson junction.

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“…1(a) can be effectively achieved in an s-wave Josephson π-junction mediated by the helical edge state of 2D TI [24][25][26][27][28]. This scheme has been under active experimental study [29][30][31][32][33]. In a Rashba nanowire, the s ± -wave pairing in Fig.…”

mentioning

confidence: 99%

“…The striking 2CK effect and their reductions in various limits can also provide fingerprints of Majorana Kramers pairs in their experimental detections. In the experiment coupling the Josephson junction and the 2D TI [29][30][31][32][33], the phase difference δφ can be controlled by a magnetic flux. If the junction is weakly probed at the two edges by the source and drain, the studied 2CK effect should be realized at δφ = π, and the discussed Zeeman-splitting scenario should apply to δφ = π.…”

mentioning

confidence: 99%

Topological Majorana Two-Channel Kondo Effect

Bao¹,

Zhang²

2017

Phys. Rev. Lett.

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A one-dimensional time-reversal-invariant topological superconductor hosts a Majorana Kramers pair at each end, where time-reversal symmetry acts as a supersymmetry that flips local fermion parity. We examine the transport anomaly of such a superconductor, floating and tunnel-coupled to normal leads at its two ends. We demonstrate the realization of a topologically-protected, channelsymmetric, two-channel Kondo effect without fine-tuning. Whereas the nonlocal teleportation vanishes, a lead present at one end telecontrols the universal transport through the other end.

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Gapless Andreev bound states in the quantum spin Hall insulator HgTe

Cited by 316 publications

References 41 publications

Detecting topological superconductivity with φ0 Josephson junctions

Detecting topological superconductivity with φ0 Josephson junctions

Quench dynamics of the Josephson current in a topological Josephson junction

Topological Majorana Two-Channel Kondo Effect

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