Effect of surface state hybridization on current-induced spin-orbit torque in thin topological insulator films

TL;DR

This paper studies how the hybridization of surface states in thin topological insulator films affects the efficiency of current-induced spin-orbit torque, identifying an optimal film thickness for maximum torque.

Contribution

It introduces a relation between spin torque and TI thickness, revealing the optimal thickness for maximizing spin-orbit torque in thin TI films.

Findings

Optimal TI thickness for maximum torque is about 3-5 nm.

Hybridization significantly influences the spin-orbit torque.

Numerical analysis confirms the optimal thickness range.

Abstract

We investigate the current-induced spin-orbit torque in thin topological insulator (TI) films in the presence of hybridization between the top and bottom surface states. We formulate the relation between spin torque and TI thickness, from which we derived the optimal value of the thickness to maximize the torque. We show numerically that in typical TI thin films made of $\mathrm{Bi_2Se_3}$, the optimal thickness is about 3-5 nm.