Theory of bi-linear magnetoresistance within the minimal model for surface states in topological insulators

TL;DR

This paper presents a theoretical model explaining bi-linear magnetoresistance in topological insulator surface states, emphasizing the role of spin polarization and scattering processes at low Fermi energies.

Contribution

It introduces a new mechanism for BMR based on second-order response, current-induced spin polarization, and defect scattering, within a minimal surface state model.

Findings

BMR depends linearly on electric and magnetic fields.

The mechanism dominates at lower Fermi energies.

Theoretical approach uses Green function formalism.

Abstract

A new mechanism of bi-linear magnetoresistance (BMR) is studied theoretically within the minimal model describing surface electronic states in topological insulators (TIs). The BMR appears as a consequence of the second-order response to electric field, and depends linearly on both electric field (current) and magnetic field. The mechanism is based on the interplay of current-induced spin polarization and scattering processes due to peculiar spin-orbit defects. The proposed mechanism is compared to that based on a Fermi surface warping, and is shown to be dominant at lower Fermi energies. We provide a consistent theoretical approach based on the Green function formalism and show that the magnetic field dependent relaxation processes in the presence of non-equilibrium current-induced spin polarization give rise to the BMR.