Spin Transfer Torque and Electric Current in Helical Edge States in Quantum Spin Hall Devices

Abstract

We study the dynamics of a quantum spin Hall edge coupled to a magnet with its own dynamics. Using spin transfer torque principles, we analyze the interplay between spin currents in the edge state and dynamics of the axis of the magnet, and draw parallels with circuit analogies. As a highlighting feature, we show that while coupling to a magnet typically renders the edge state insulating by opening a gap, in the presence of a small potential bias, spin-transfer torque can restore perfect conductance by transferring angular momentum to the magnet. In the presence of interactions within the edge state, we employ a Luttinger liquid treatment to show that the edge, when subject to a small voltage bias, tends to form a unique dynamic rotating spin wave state that naturally couples into the dynamics of the magnet. We briefly discuss realistic physical parameters and constraints for observing this interplay between quantum spin Hall and spin-transfer torque physics.

6 pages, 2 figures

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• Noiseless manipulation of helical edge state transport by a quantum magnet
• Topological electric driving of magnetization dynamics in insulators
• Signatures of Jackiw-Rebbi resonance in the thermal conductance of topological Josephson junctions with magnetic islands
• Protection of Edge transport in Quantum Spin Hall samples: Spin-Symmetry Based General Approach and Examples
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• Detailed study of nonlinear cooling with two-terminal configurations of topological edge states
• Current-induced switching of magnetic molecules on topological insulator surfaces
• Suppression of ballistic helical transport by isotropic dynamical magnetic impurities
• Anomalous quantum Hall effect induced by disorder in topological insulators
• Long-range spin transport on the surface of topological Dirac semimetal
• Heat-to-motion conversion for quantum active matter
• Quantum transport phenomena induced by time-dependent fields
• Interference effects induced by a precessing easy-plane magnet coupled to a helical edge state
• Enhanced lifetimes of spin chains coupled to chiral edge states
• Finite-frequency admittance and noise of a helical edge coupled to a magnet