Current-Induced Gap Opening in Interacting Topological Insulator Surfaces

Ajit C. Balram, Karsten Flensberg, Jens Paaske, and Mark S. Rudner

Phys. Rev. Lett. 123, 246803 – Published 11 December 2019

Abstract

Two-dimensional topological insulators (TIs) host gapless helical edge states that are predicted to support a quantized two-terminal conductance. Quantization is protected by time-reversal symmetry, which forbids elastic backscattering. Paradoxically, the current-carrying state itself breaks the time-reversal symmetry that protects it. Here we show that the combination of electron-electron interactions and momentum-dependent spin polarization in helical edge states gives rise to feedback through which an applied current opens a gap in the edge state dispersion, thereby breaking the protection against elastic backscattering. Current-induced gap opening is manifested via a nonlinear contribution to the system’s $I - V$ characteristic, which persists down to zero temperature. We discuss prospects for realizations in recently discovered large bulk band gap TIs, and an analogous current-induced gap opening mechanism for the surface states of three-dimensional TIs.

Received 4 February 2019

DOI:https://doi.org/10.1103/PhysRevLett.123.246803

Physics Subject Headings (PhySH)

Topological insulators Topological phases of matter

Topological materials

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Ajit C. Balram ^1,2,3, Karsten Flensberg², Jens Paaske², and Mark S. Rudner^1,2

¹Niels Bohr International Academy, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
²Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
³The Institute of Mathematical Sciences, HBNI, CIT Campus, Chennai 600113, India