SU(2) Non-Abelian Holonomy and Dissipationless Spin Current in Semiconductors

TL;DR

This paper provides an exact quantum mechanical calculation of the dissipationless spin Hall effect in p-type semiconductors, revealing a non-abelian gauge field and monopole structure in momentum space that lead to a conserved spin current.

Contribution

It introduces an exact quantum approach to the spin Hall effect, incorporating non-abelian gauge fields and monopole structures, advancing understanding beyond semiclassical models.

Findings

Identification of an exactly conserved spin current in the presence of spin-orbit coupling.

Discovery of a monopole structure in momentum space related to the spin Hall effect.

Quantum correction to previous semiclassical results on spin current.

Abstract

Following our previous work [S. Murakami, N. Nagaosa, S. C. Zhang, Science 301, 1348 (2003)] on the dissipationless quantum spin current, we present an exact quantum mechanical calculation of this novel effect based on the linear response theory and the Kubo formula. We show that it is possibxle to define an exactly conserved spin current, even in the presence of the spin-orbit coupling in the Luttinger Hamiltonian of p-type semiconductors. The light- and the heavy-hole bands form two Kramers doublets, and an SU(2) non-abelian gauge field acts naturally on each of the doublets. This quantum holonomy gives rise to a monopole structure in momentum space, whose curvature tensor directly leads to the novel dissipationless spin Hall effect, i.e., a transverse spin current is generated by an electric field. The result obtained in the current work gives a quantum correction to the spin current obtained in the previous semiclassical approximation.