Intrinsic spin Hall effect in topological insulators: A first-principles study

TL;DR

This study uses first-principles calculations to evaluate the intrinsic spin Hall conductivity of topological insulators, revealing finite values near the Fermi energy and implications for spintronic applications.

Contribution

It provides the first-principles analysis of spin Hall conductivity in topological insulators, highlighting the bulk contribution and comparing it with experimental data.

Findings

Finite spin Hall conductivity of 100-200 (ħ/2e) S/cm near Fermi energy

Bulk contribution to spin current is comparable to surface effects

Spin Hall angles are significant despite lower conductivity than heavy metals

Abstract

The intrinsic spin Hall conductivity of typical topological insulators Sb$_2$Se$_3$, Sb$_2$Te$_3$, Bi$_2$Se$_3$, and Bi$_2$Te$_3$ in the bulk form, is calculated from first-principles by using density functional theory and the linear response theory in a maximally localized Wannier basis. The results show that there is a finite spin Hall conductivity of 100--200 ($\hbar$/2e)(S/cm) in the vicinity of the Fermi energy. Although the resulting values are an order of magnitude smaller than that of heavy metals, they show a comparable spin Hall angle due to their relatively lower longitudinal conductivity. The spin Hall angle for different compounds are then compared to that of recent experiments on topological-insulator/ferromagnet heterostructures. The comparison suggests that the role of the bulk in generating a spin current and consequently a spin torque in magnetization switching applications is comparable to that of the surface including the spin-momentum locked surface states and the Rashba-Edelstein effect at the interface.