Theory of current-driven dynamics of spin textures on the surface of a topological insulator

Abstract

Spin-transfer torque is one of the important physical quantities to understand for successful application of topological insulators to spintronics. In this paper, we present analytical expressions of the spin-transfer torques on a surface of a magnetic topological insulator by including the higher-order contributions of momentum, k 2 -term and the hexagonal warping. We obtain six different types of the spin-transfer torque including both the field-like and the damping-like torques; the four of them appear only when the higher-order momentum contributions are included. In addition, we discuss the dynamics of magnetic skyrmions driven by the spin-transfer torques on the surface of the topological insulator. Unlike the skyrmion dynamics in conventional metals, we find that the dynamics significantly depends on the internal structure of magnetic textures.

Spin-dependent transport through a Weyl semimetal surface

“…In some sense, our experiment resembles ones on ferromagnetic multilayers, where spin-dependent scattering affects the magnetic moments of the spin-polarized layers, while their mutual orientation defines the differential resistance [15][16][17][18][19][20][21] . It might be natural 28,29 , that we B (T) observe similar dV /dI(I) characteristics.…”

Torque field and skyrmion movement by spin transfer torque in a quasi-2d interface in presence of strong spin-orbit interaction

“…In this work we consider the second case therefore this field is pointing in the material growth direction ẑ. On the other hand, in a topological insulator the origin of the linear term in eq.6 is the electron kinetic energy while the quadratic term arises as second order corrections to non-ideal materials 25 .…”

“…These two materials (semiconductors and TI's ) imply a quantum mechanical model for the current because the more interesting properties of these materials arise in the regime of conduction by a single electronic mode. Very few works have considered quantum mechanical models for the current to calculate the spin torque [22][23][24] in general or TI's in particular as in ref. 25 where an analytical approach was chosen where the effect of boundaries was not considered.…”

“…Very few works have considered quantum mechanical models for the current to calculate the spin torque [22][23][24] in general or TI's in particular as in ref. 25 where an analytical approach was chosen where the effect of boundaries was not considered. In this work we will also restrict ourselves to STT where the spin current flows in the interface plane.…”

Non-linear antidamping spin-orbit torque originating from intra-band transport on the warped surface of a topological insulator

“…Theoretically, there have been many efforts to explain the emergence of large SOTs, especially the antidamping component, at the magnetic surfaces of topological insulators using linear response theory. Garate and Franz [28,29] ascribed the SOTs in FM/TI bilayers to a topological magnetoelectric effect with emphasis on its dissipationless Hall current for Fermi energies in the Dirac gap. Extending it to finite Fermi energies, this dissipationless damping was also found to arise from intrinsic inter-band transitions [30][31][32][33].…”