SKM 2021 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 12: Focus Session: Spin-Charge Interconversion (joint session MA/HL)

HL 12.6: Invited Talk

Tuesday, September 28, 2021, 16:15–16:45, H5

Nonlinear magnetoresistance and Hall effect from spin-momentum locking — •Giovanni Vignale — University of Missouri

Surface states of topological insulators exhibit the phenomenon of spin-momentum locking, whereby the orientation of an electron spin is determined by its momentum. Recently a link has been discovered between the spin texture of these states and a new type of nonlinear magnetoresistance, which depends on the relative orientation of the current with respect to the magnetic field as well as the crystallographic axes, and scales linearly with both the applied electric and magnetic fields. The nonlinear magnetoresistance originates from the conversion of a non-equilibrium spin current into a charge current under the application of an external magnetic field. Additionally, it has been found that the nonlinear planar Hall effect, manifested as a transverse component of the nonlinear current, exhibits a Pi/2 phase shift with respect to the nonlinear longitudinal current, in marked contrast to the usual Pi/4 phase difference that exists between the linear planar Hall current and the linear longitudinal current in typical topological insulators and transition metal ferromagnets. In this talk I review the development of the theory vis-a-vis experiments done on the surface of topological insulator Bi_2Se_3 films and other materials.