Non-local Chemical Potential Modulation in Topological Insulators Via Electric Field Driven Trapped Charge Migration

TL;DR

This paper introduces a novel in-situ method to non-locally modulate the chemical potential in topological insulator nanoribbons using electric field-driven charge migration, surpassing traditional gating techniques.

Contribution

The authors demonstrate a simple, effective technique for large, non-local chemical potential tuning in TIs via electric fields, enabling new experimental possibilities.

Findings

Chemical potential can be shifted across the Dirac point within and outside the channel.

Charge hopping among defect states causes the non-local modulation.

Photocurrent mapping supports the charge migration mechanism.

Abstract

Topological insulators (TIs) host unusual surface states with Dirac dispersion and helical spin texture and hold high potentials for novel applications in spintronics and quantum computing. Control of the chemical potential in these materials is challenging but crucial to realizing the hotly pursued exotic physics, including efficient spin generation1,2, Majorana Fermions3-5, and exciton condensation6,7. Here we report a simple and effective method that can in-situ tune the chemical potential of single-crystal Bi2-xSbxSe3 nanoribbons, with a magnitude significantly larger than traditional electrostatic gating. An electric field parallel to a device channel can shift the chemical potential across the Dirac point, both inside and outside the channel. We attribute this non-local reversible modulation of chemical potential to electric-field-induced charge hopping among defect states, further supported by photocurrent mapping. Our approach enables engineering chemical potential distributions in TIs and opens up tremendous opportunities for investigating fundamental transport mechanisms of charge and composite particles in these materials.