Robust Fabry-Perot interference in dual-gated Bi$_2$Se$_3$ devices

TL;DR

This paper investigates Fabry-Perot interference in hybrid topological insulator devices, revealing phase coherent surface state transport and tunability via electrostatic gating, with implications for Majorana fermions.

Contribution

It demonstrates tunable Fabry-Perot interference in dual-gated Bi$_2$Se$_3$ devices, highlighting surface state coherence and electrostatic coupling effects.

Findings

Conductance oscillations of ~0.1 e^2/h observed

Oscillations are independent of bulk carrier density

Interference can be tuned by top and back gates

Abstract

We study Fabry-Perot interference in hybrid devices, each consisting of a mesoscopic superconducting disk deposited on the surface of a three-dimensional topological insulator. Such structures are hypothesized to contain protected zero modes known as Majorana fermions bound to vortices. The interference manifests as periodic conductance oscillations of magnitude $\sim 0.1$ $e^2/h$. These oscillations show no strong dependence on bulk carrier density or sample thickness, suggesting that they result from phase coherent transport in surface states. However, the Fabry-Perot interference can be tuned by both top and back gates, implying strong electrostatic coupling between the top and bottom surfaces of topological insulator.