Gate-Controlled Supercurrent in Epitaxial Al/InAs Nanowires

Abstract

Gate-controlled supercurrent (GCS) in superconducting nanobridges has recently attracted attention as a means to create superconducting switches. Despite the clear advantages for applications, the microscopic mechanism of this effect is still under debate. In this work, we realize GCS for the first time in a highly crystalline superconductor epitaxially grown on an InAs nanowire. We show that the supercurrent in the epitaxial Al layer can be switched to the normal state by applying ≃±23 V on a bottom gate insulated from the nanowire by a crystalline hBN layer. Our extensive study of the temperature and magnetic field dependencies suggests that the electric field is unlikely to be the origin of GCS in our device. Though hot electron injection alone cannot explain our experimental findings, a very recent non-equilibrium phonons based picture is compatible with most of our results.

Electrostatic Field-Driven Supercurrent Suppression in Ionic-Gated Metallic Superconducting Nanotransistors

“…Recently, gate voltage (V g ) induced bipolar full supercurrent suppression was demonstrated via conventional solid gating in several metallic superconducting nanostructures, such as wires, 3,4 constriction Josephson junctions, 5 and proximitized normal metals. 6 Similar results were also obtained on suspended 7 and epitaxial 8 superconducting metal layers grown on semiconductor nanowires. Differently from charge accumulation/depletion, this gating effect also seems to influence the phase of the Cooper pair condensate 9−11 without apparent impact on T C and R N , 12 thereby suggesting a nontrivial interaction between electrostatic fields and superconductivity.…”

Destroying superconductivity in thin films with an electric field

“…For strong enough electric fields normal metal behaviour was observed. This phenomenon is known as the Superconductive Field Effect (SFE) and the results have been recently confirmed by other experimental groups [5][6][7][8][9][10][11].…”

“…The microscopic origin of this phenomenon is unclear. All the materials [2,[5][6][7][8][9][10][11] analyzed are well described by the conventional BCS theory and metallic in the normal phase (hence it is surprising that the electrostatic field could play any role). It has been suggested that energetic quasi-particle injection from the gate control [6,7] or energy or phase fluctuations [9] could be responsible for the observations.…”

“…Alternate microscopic proposals have been suggested to explain the experimental results of [2,[5][6][7][8][9][10][11]. These include electric-field induced spin-orbit polarization [13], Rashba-like surface effects [14] and the excitation of an exotic superconducting state due to Schwinger-like effects [15].…”

Electrostatic field-driven supercurrent suppression in ionic-gated metallic Josephson nanotransistors

“…Recently, gate voltage (V g ) induced bipolar full supercurrent suppression was demonstrated via conventional solid gating in several metallic superconducting nanostructures, such as wires [3], constriction Josephson junctions [4], and proximitized normal metals [5]. Similar results were obtained also on suspended [6] and epitaxial [7] superconducting metal layers grown on semiconductor nanowires. Differently from charge accumulation/depletion, this gating effect seems to influence as well the phase of the Cooper pairs condensate [8][9][10] without apparent impact on T C and R N [11], thereby suggesting a non-trivial interaction between electrostatic fields and superconductivity.…”