Spin-orbit torque in two-dimensional antiferromagnetic topological insulators

Abstract

We investigate spin transport in two-dimensional ferromagnetic (FTI) and antiferromagnetic (AFTI) topological insulators. In the presence of an in-plane magnetization AFTI supports zero energy modes, which enables topologically protected edge conduction at low energy. We address the nature of current-driven spin torque in these structures and study the impact of spin-independent disorder. Interestingly, upon strong disorder the spin torque develops an antidamping component (i.e., even upon magnetization reversal) along the edges, which could enable current-driven manipulation of the antiferromagnetic order parameter. This antidamping torque decreases when increasing the system size and when the system enters the trivial insulator regime.

Current-induced spin-orbit torques in ferromagnetic and antiferromagnetic systems

“…These studies reveal that SOT experiences a significant enhancement depending on the topological phase (Li and Manchon, 2016;Mahfouzi et al, 2010): the emergence of edge currents promotes a quantized charge pumping when the magnetization is perpendicular to the plane. Such investigations have been recently extended to AF 2D topological insulators, where a time-reversal combined with a half unit cell translation is a symmetry of the system which preserves topological protection, despite the broken time-reversal symmetry of the magnetic state (Ghosh and Manchon, 2017a).…”

Spin glass transition in a thin-film NiO/permalloy bilayer

“…They have recently attracted a renewed attention thanks to the high dynamical magnetization frequencies of AFs, enabling applications in fast interconversion and transmission of spin signals [3], and THz optics [4]. Additionally, vanishing magnetization of AFs can enable enhanced spin-transfer efficiency in electronic manipulation of the magnetic states for ultrahigh-density information storage, avoiding the constraints imposed by the angular momentum conservation and the dipolar fields ubiquitous to ferromagnetic systems [5].A number of novel phenomena have been recently observed or predicted for thin AF films, including antiferromagnetic spin-orbit torques [6][7][8], AF magnetoresistance [9], enhanced interconversion between electron spin current and spin waves [3,10], generation of THz signals [4,11], AF exchange springs [12,13], and topological effects [14][15][16]. While some of these phenomena are expected even for standalone AFs, strong exchange coupling at AF/F interfaces provides one of the most efficient approaches to controlling and analyzing the magnetization states of AFs, with the state of F controlled by the magnetic field or spin current, and characterized by the magnetoelectronic or optical techniques.…”

Spin-orbit torques in a Rashba honeycomb antiferromagnet

“…The right-hand sides of Eqs. (20) contain the quantities that can be called generalized torques. Here we are only interested in specific contributions to generalized torques that are induced by the chemical potential difference δµ = eV bias between left and right leads.…”

“…Indeed, for an "isotropic" antiferromagnet we find, in complete analogy with Eqs. (20), the equations of motioṅ…”