Persistent Optical Gating of a Topological Insulator

TL;DR

This paper introduces a novel all-optical method for persistent, bidirectional gating of topological insulators, enabling dynamic patterning of electronic structures without degrading material quality.

Contribution

The authors develop an optical technique to controllably and permanently modify the charge distribution in a topological insulator, allowing reconfigurable electronic patterning.

Findings

Optical gating induces persistent charge redistribution in TI.

Patterned p-n junctions are visualized via scanning photocurrent microscopy.

Method enables dynamic, non-destructive reconfiguration of TI electronic properties.

Abstract

Topological insulators (TIs) have attracted much attention due to their spin-polarized surface and edge states, whose origin in symmetry gives them intriguing quantum-mechanical properties. Robust control over the chemical potential of TI materials is important if these states are to become useful in new technologies, or as a venue for exotic physics. Unfortunately, chemical potential tuning is challenging in TIs in part because the fabrication of electrostatic top-gates tends to degrade material properties and the addition of chemical dopants or adsorbates can cause unwanted disorder. Here, we present an all-optical technique which allows persistent, bidirectional gating of a (Bi,Sb)2Te3 channel by optically manipulating the distribution of electric charge below its interface with an insulating SrTiO3 substrate. In this fashion we optically pattern p-n junctions in a TI material, which we subsequently image using scanning photocurrent microscopy. The ability to dynamically write and re-write mesoscopic electronic structures in a TI may aid in the investigation of the unique properties of the topological insulating phase. The optical gating effect may be adaptable to other material systems, providing a more general mechanism for reconfigurable electronics.