Superconducting proximity effect in inverted InAs/GaSb quantum well structures with Ta electrodes

Abstract

We present our recent electronic transport results in top-gated InAs/GaSb quantum well hybrid structures with superconducting Ta electrodes. We show that the transport across the InAs−Ta junction depends largely on the interfacial transparency, exhibiting distinct zero-bias behavior.For a relatively resistive interface a broad conductance peak is observed at zero bias. When a transparent InAs−Ta interface is achieved, a zero-bias conductance dip appears with two coherent-peak-like features forming at bias voltages corresponding to the superconducting gap of Ta. The conductance spectra of the transparent InAs−Ta junction at different gate voltages can be fit well using the standard Blonder-Tinkham-Klapwijk theory.

Interlayer current near the edge of an InAs/GaSb double quantum well in proximity with a superconductor

“…We can also support this conclusion by data known from literature [11][12][13] . The transition from the bulk to edge Josephson supercurrent was reported in Ref.…”

“…Since the edge effects are of primary importance in InAs/GaSb bilayers 4,[6][7][8][9][10][11][12][13] , we fabricate side superconductor-normal (NS) junctions 25,26 by sputtering 50 nm thick Nb or NbN film over the mesa step, see Fig. 1.…”

“…Supposed to be topological, this one-dimensional edge transport is a subject of continuous attention 4,[6][7][8][9][10] . In proximity with a superconductor, it is regarded [11][12][13] to be suitable for Majorana fermion investigations 14 .…”

Induced superconductivity in high-mobility two-dimensional electron gas in gallium arsenide heterostructures

“…Induced superconductivity and electrostatic control of critical current has been demonstrated in two-dimensional gases in InAs [2,3], graphene [4] and topological insulators [5? -8], and in onedimensional systems [9][10][11] including quantum spin Hall edges [12,13]. Recently, interest in superconductor-semiconductor interfaces was renewed by the search for Majorana fermions [14,15], which were predicted to reside at the interface [16][17][18].…”

Non-triviality matters

“…So even when the devices are fabricated by the same procedure, a variation in the barrier resistance, that naturally occurs in the growth procedure, can re- sult in the observed differences around zero voltage [168]. The existence of both zero conductance peaks and dips is also observed experimentally in semiconductor/superconductor [168,169], graphene/superconductor [170] and in topological insulator/superconductor devices [171,172]. The conductance dip at ∆ ST I is reproduced in all three the devices.…”