Top-down fabrication of bulk-insulating topological insulator nanowires for quantum devices

TL;DR

This paper introduces a scalable top-down fabrication method for bulk-insulating topological insulator nanowires from high-quality films, enabling chemical potential tuning and demonstrating key quantum effects relevant for Majorana states.

Contribution

The authors develop a novel top-down fabrication process for high-quality, bulk-insulating topological insulator nanowires with tunable chemical potential and observe quantum effects and superconducting proximity.

Findings

Chemical potential can be tuned to charge neutrality point.

Resistance oscillations as functions of gate voltage and magnetic field.

Superconducting proximity effect observed in the nanowires.

Abstract

In a nanowire (NW) of a three-dimensional topological insulator (TI), the quantum-confinement of topological surface states leads to a peculiar subband structure that is useful for generating Majorana bound states. Top-down fabrication of TINWs from a high-quality thin film would be a scalable technology with great design flexibility, but there has been no report on top-down-fabricated TINWs where the chemical potential can be tuned to the charge neutrality point (CNP). Here we present a top-down fabrication process for bulk-insulating TINWs etched from high-quality (Bi$_{1-x}$Sb$_{x}$)$_2$Te$_3$ thin films without degradation. We show that the chemical potential can be gate-tuned to the CNP and the resistance of the NW presents characteristic oscillations as functions of the gate voltage and the parallel magnetic field, manifesting the TI-subband physics. We further demonstrate the superconducting proximity effect in these TINWs, preparing the groundwork for future devices to investigate Majorana bound states.