Topological insulator single-electron transistors for charge sensing applications

TL;DR

This paper demonstrates topological insulator-based single-electron transistors as sensitive charge sensors compatible with magnetic fields, showing Coulomb blockade effects and charge shifts influenced by magnetic fields, with potential for Majorana mode detection.

Contribution

The work introduces TI-based SETs as charge sensors with magnetic-field compatibility and characterizes their charge sensitivity and magnetic response, advancing TI hybrid device integration.

Findings

Observation of Coulomb diamonds confirming charge quantization.

Detection of persistent Coulomb resonance shifts up to e/2 charge.

Magnetic field dependence consistent with Zeeman effect on trap states.

Abstract

We present topological insulator (TI)-based single-electron transistors (SETs) as magnetic-field-compatible charge sensing devices that are easily integrable with TI-superconductor hybrid platforms. We observe well-resolved Coulomb diamonds in the charge-stability diagrams of our devices confirming the charge quantization and single-electron transport. In some devices, the Coulomb resonances show persistent shifts corresponding up to $\sim$ e/2 charge. An axial magnetic field further displaces these shifts to higher or lower gate voltages. We find that the axial magnetic-field dependence of the shifts is consistent with the Zeeman shift of a trap state coupled to the SET, and we reproduce the observations using numerical simulations. The resonance shifts are therefore identified as a consequence of the sensitivity of our TI-SET devices to charges in proximity. Establishing this charge sensing capability is a first step toward integrating TI-SETs as charge sensors in more complex TI-based hybrid devices, with the overarching goal of detecting and braiding Majorana zero modes.