Non-Adiabatic Spin-Induced Currents in Magnetic Weyl Semimetals

Abstract

We theoretically study dc electric currents induced by rapid spin precession in noncentrosymmetric magnetic Weyl semimetals using the Floquet--Keldysh Green's-function formalism. The spin dynamics act as a time-dependent chiral gauge field and the geometric structure of electric currents is expressed in terms of the Berry curvature, the quantum metric, and the shift vector. For an isotropic Weyl cone, only an injection current is generated. This current scales quadratically with the driving frequency and linearly with the relaxation time associated with coupling to a fermionic bath. We further show that a finite Weyl-cone tilt modifies the available interband-transition phase space, smooths the frequency dependence of the current, and allows for a shift current and another type of injection current, both of which flow in directions determined by the tilt and the direction of the precession. A finite net current can remain after summing contributions from Weyl nodes of opposite chiralities when their transition phase spaces are inequivalent.