Observation of the superconducting proximity effect and possible evidence for Pearl vortices in a candidate topological insulator

TL;DR

This study demonstrates the superconducting proximity effect in Bi2Se3 nanoribbons with tungsten contacts, revealing ballistic surface transport and possible Pearl vortices, advancing understanding of topological insulator-superconductor interfaces.

Contribution

It provides experimental evidence of proximity-induced superconductivity in topological insulator nanoribbons and suggests the formation of Pearl vortices under magnetic fields.

Findings

Supercurrent and multiple Andreev reflections observed over long channel lengths.

Magnetoresistance oscillations periodic in magnetic field indicating vortex formation.

Evidence for Pearl vortices in proximity-induced superconducting regions.

Abstract

We report the observation of the superconducting proximity effect in nanoribbons of a candidate topological insulator (Bi2Se3) which is interfaced with superconducting (tungsten) contacts. We observe a supercurrent and multiple Andreev reflections for channel lengths that are much longer than the inelastic and diffusive thermal lengths deduced from normal state transport. This suggests that the proximity effect couples preferentially to a ballistic surface transport channel, even in the presence of a coexisting diffusive bulk channel. When a magnetic field is applied perpendicular to the plane of the nanoribbon, we observe magnetoresistance oscillations that are periodic in magnetic field. Quantitative comparison with a model of vortex blockade relates the occurrence of these oscillations to the formation of Pearl vortices in the region of proximity induced superconductivity.