High characteristic voltages in Nb/p-type InAs/Nb Josephson junctions

Chrestin, A.; Merkt, U.

doi:10.1063/1.119116

Cited by 16 publications

(11 citation statements)

References 15 publications

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“…S4). This high transparency is in line with the best results ever achieved for micrometer-scale superconductor-semiconductor interfaces (22). Besides an overall conductance enhancement, the sub-gap regime is characterized by a series of peaks in dI/dV occurring at V = Fig.…”

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confidence: 87%

Tunable Supercurrent Through Semiconductor Nanowires

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Dam

Roest

et al. 2005

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Nanoscale superconductor/semiconductor hybrid devices are assembled from indium arsenide semiconductor nanowires individually contacted by aluminum-based superconductor electrodes. Below 1 kelvin, the high transparency of the contacts gives rise to proximity-induced superconductivity. The nanowires form superconducting weak links operating as mesoscopic Josephson junctions with electrically tunable coupling. The supercurrent can be switched on/off by a gate voltage acting on the electron density in the nanowire. A variation in gate voltage induces universal fluctuations in the normal-state conductance, which are clearly correlated to critical current fluctuations. The alternating-current Josephson effect gives rise to Shapiro steps in the voltage-current characteristic under microwave irradiation.

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confidence: 87%

Tunable Supercurrent Through Semiconductor Nanowires

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Roest

et al. 2005

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“…In addition to the use of true heterostructures, some investigators have employed, as the coupling medium, the 2-D electron gas (2DEG) in the n-type surface inversion layer naturally present on bulk p-type InAs, 17,[22][23][24] a possibility already recognized by Silver et al The only truly successful work of this kind was that by Chrestin and Merkt, 24 who recently used Nb electrodes with separations down to 20 nm, at which point the inherent limitations of the inversion layer scheme (low electron sheet concentrations and strong surface scattering) are largely overcome by the proximity of the electrodes.…”

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confidence: 99%

Current-voltage characteristics of semiconductor-coupled superconducting weak links with large electrode separations

et al. 1998

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We have studied the current-voltage characteristics of superconducting weak links in which the coupling medium is the 2-D electron gas in InAs-based semiconductor quantum wells, with relatively large (typically 0.5µm) separations between niobium electrodes. The devices exhibit Josephson-like current-voltage characteristics; however, the falloff of the differential resistance with decreasing temperature is thermally activated, and is orders of magnitude slower than for more conventional weak links. Most unexpectedly, the thermal activation energies are found to be proportional to the width of the device, taken perpendicular to the current flow. This behavior falls outside the range of established theories; we propose that it is a fluctuation effect caused by giant shot noise associated with multiple Andreev reflections. The possibility of non-equilibrium effects is discussed.

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“…Such structures, reviewed in Ref. [25], have been realized by contacting InAs surface inversion layers [26,27] We show how to design and control MBS in a pS system with a stripe of the superconducting layer removed to form an effective one-dimensional topological supercon- ductor. This forms a pS-N-pS junction as sketched in Fig.…”

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“…Such structures, reviewed in Ref. [25], have been realized by contacting InAs surface inversion layers [26,27] or InAs/InGaAs heterostructures [28,29] with superconducting Nb or Al. Recently, it has become possible to grow an Al top layer epitaxially [24], forming a clean interface with the 2DEG.…”

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Two-Dimensional Platform for Networks of Majorana Bound States

2017

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We model theoretically a two-dimensional electron gas (2DEG) covered by a superconductor and demonstrate that topological superconducting channels are formed when stripes of the superconducting layer are removed. As a consequence, Majorana bound states (MBS) are created at the ends of the stripes. We calculate the topological invariant and energy gap of a single stripe, using realistic values for an InAs 2DEG proximitized by an epitaxial Al layer. We show that the topological gap is enhanced when the structure is made asymmetric. This can be achieved by either imposing a phase difference (by driving a supercurrent or using a magnetic-flux loop) over the strip or by replacing one superconductor by a metallic gate. Both strategies also enable control over the MBS splitting, thereby facilitating braiding and readout schemes based on controlled fusion of MBS. Finally, we outline how a network of Majorana stripes can be designed.PACS numbers: 71.10. Pm, 74.50.+r, Majorana bound states (MBS) are states localized at the edges of topological superconductors [1][2][3][4]. They have nonlocal properties that may be utilized for storage and manipulation of quantum information in a topologically protected way [5][6][7]. However, the realization of MBS requires superconducting p-wave pairing, which appears only in exotic materials. Therefore, there is currently a search for ways to engineer p-wave pairing by combining s-wave superconductors with strong spinorbit materials. Recent experiments looked for evidence of MBS in, for example, semiconducting nanowires [8][9][10][11][12][13][14], topological insulators [15], and magnetic atom chains [16, 17]. These systems may also allow demonstration experiments of the nonlocal properties of MBS, for example using recent suggestions for controlling MBS in prototypical architectures [18][19][20][21][22][23]. However, to go beyond basic demonstration experiments a scalable and flexible platform for large-scale MBS networks is needed.Here, we suggest one such flexible platform based on a two-dimensional electrons gas (2DEG) with strong spinorbit coupling in proximity to a superconductor [24]. Such structures, reviewed in Ref. [25], have been realized by contacting InAs surface inversion layers [26,27] We show how to design and control MBS in a pS system with a stripe of the superconducting layer removed to form an effective one-dimensional topological supercon- ductor. This forms a pS-N-pS junction as sketched in Fig. 1(a), which can be fabricated by standard lithographic techniques. We show, similar to other semiconductorbased setups [34][35][36][37][38], that this system undergoes several topological phase transitions when increasing a magnetic field parallel to the stripe for parameters readily available in the lab. We base our findings on a numerical tightbinding calculation of the energy spectrum, the topological invariant, as well as transport calculations [33]. We discuss how the topological energy gap depends on various parameters, which is vital for the topological protection ...

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High characteristic voltages in Nb/p-type InAs/Nb Josephson junctions

Cited by 16 publications

References 15 publications

Tunable Supercurrent Through Semiconductor Nanowires

Tunable Supercurrent Through Semiconductor Nanowires

Current-voltage characteristics of semiconductor-coupled superconducting weak links with large electrode separations

Two-Dimensional Platform for Networks of Majorana Bound States

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