N\'eel Spin-Orbit Torque in Antiferromagnetic Quantum Spin and Anomalous Hall Insulators

TL;DR

This paper introduces a novel Nel spin-orbit torque mechanism in antiferromagnetic topological insulators, enabling efficient, Joule-heating-free control of AFM dynamics via electric fields and microwaves.

Contribution

It extends the Kane-Mele model to include AFM order, revealing a new bulk Nel spin-orbit torque driven by pure adiabatic currents in topological insulators.

Findings

Demonstrates a Nel spin-orbit torque arising from topological phases.

Shows microwave-driven AFM resonance can be significantly enhanced.

Reveals a Joule-heating-free mechanism for ultrafast AFM control.

Abstract

Interplay between magnetic ordering and topological electrons not only enables new topological phases but also underpins electrical control of magnetism. Here we extend the Kane-Mele model to include the exchange coupling to a collinear background antiferromagnetic (AFM) order, which can describe transition metal trichalcogenides. Owing to the spin-orbit coupling and staggered on-site potential, the system could exhibit the quantum anomalous Hall and quantum spin Hall effects in the absence of a net magnetization. Besides the chiral edge states, these topological phases support a staggered Edelstein effect through which an applied electric field can generate opposite non-equilibrium spins on the two AFM sublattices, realizing the N\'eel-type spin-orbit torque (NSOT). Contrary to known NSOTs in AFM metals driven by conduction currents, our NSOT arises from pure adiabatic currents devoid of Joule heating, while being a bulk effect not carried by the edge currents. By virtue of the NSOT, the electric field of a microwave can drive the AFM dynamics with a remarkably high efficiency. Compared to the ordinary AFM resonance driven by the magnetic field, the new mechanism can enhance the resonance amplitude by more than one order of magnitude and the absorption rate of the microwave power by over two orders of magnitude. Our findings unravel an incredible way to exploit AFM topological phases to achieve ultrafast magnetic dynamics.