Quantum unidirectional magnetoresistance

TL;DR

This paper predicts a quantum interference-based unidirectional magnetoresistance effect in a bilayer of nonmagnetic metal and ferromagnetic insulator, where resistances depend on electric field direction and magnetization orientation.

Contribution

It introduces a novel quantum interference mechanism causing unidirectional magnetoresistance in bilayers, highlighting wave nature effects in magnetotransport.

Findings

Unidirectional magnetoresistance depends on electron wave interference.

Decay lengths are on the scale of the Fermi wavelength.

Effect arises from spin rotation and phase shifts at the interface.

Abstract

We predict unidirectional magnetoresistance effects arising in a bilayer composed of a nonmagnetic metal and a ferromagnetic insulator, whereby both longitudinal and transverse resistances vary when the direction of the applied electric field is reversed or the magnetization of the ferromagnetic layer is rotated. In the presence of spin-orbit coupling, an electron wave incident on the interface of the bilayer undergoes a spin rotation and a momentum-dependent phase shift. Quantum interference between the incident and reflected waves furnishes the electron with an additional velocity that is even in the in-plane component of the electron's wavevector, giving rise to quadratic magnetotransport that is rooted in the wave nature of electrons. The corresponding unidirectional magnetoresistances exhibit decay lengths at the scale of the Fermi wavelength$-$distinctive signatures of the quantum nonlinear magnetotransport effect.