Spin and Valley Hall effects induced by asymmetric interparticle scattering

TL;DR

This paper develops a theory for spin and valley Hall effects caused by asymmetric interparticle scattering in 2D systems, revealing suppression in electrons and enhancement in bosons, with implications for non-Fermi liquid behavior.

Contribution

It introduces a third-order collision integral accounting for spin-orbit coupling and asymmetric scattering, highlighting distinct effects in fermions and bosons.

Findings

Spin and valley currents are suppressed in electrons, proportional to temperature or density.

Degenerate bosons exhibit exponentially enhanced spin/valley currents with increasing density.

Results suggest non-Fermi liquid properties due to skew scattering effects.

Abstract

We develop the theory of the spin and valley Hall effects in two-dimensional systems caused by asymmetric -- skew -- scattering of the quasiparticles. The collision integral is derived in the third order in the particle-particle interaction with account for the spin-orbit coupling both for bosons and fermions. It is shown that the scattering asymmetry appears only in the processes where the interaction between the particles in the initial and intermediate state is present. We show that for degenerate electrons or nondegenerate particles the spin and valley currents induced by interparticle collisions are suppressed with their steady-state values being proportional to the squared temperature or density, respectively. Our results imply non-Fermi liquid properties of electrons in the presence of electron-electron skew scattering. Strong deviations from conventional picture of interparticle scattering are also demonstrated for the skew scattering of two-dimensional degenerate bosons, e.g. excitons or exciton polaritons: The spin or valley current of degenerate bosons contains the enhancement factor exponentially growing with increase in the particle density.