Abstract. Spin and charge currents in systems with Rashba or Dresselhaus spin–orbit couplings are formulated in a unified version of four-dimensional SU(2) × U(1) gauge theory, with U(1) being the Maxwell field and SU(2) being the Yang–Mills field. While the bare spin current is non-conserved, it is compensated by a contribution from the SU(2) gauge field, which gives rise to a spin torque in the spin transport, consistent with the semi-classical theory of Culcer et al. Orbit current is shown to be non-conserved in the presence of electromagnetic fields. Similar to the Maxwell field inducing forces on charge and charge current, we derive forces acting on spin and spin current induced by the Yang–Mills fields such as the Rashba and Dresselhaus fields and the sheer strain field. The spin density and spin current may be considered as a source generating Yang–Mills field in certain condensed matter systems.

PACS numbers: 72.25.−b, 72.10.−d, 03.65.−w

A corrigendum for this article has been published in 2006 J. Phys. A: Math. Gen. 39 11129

Print publication: Issue 22 (2 June 2006)
Received 9 November 2005
Published 16 May 2006