Gauge covariance and spin-current conservation in the gauge-field formulation of systems with spin-orbit coupling (Q2880359)

Spintronics is an emerging research direction in sold-state physics. An important issue in spintronics is a spin current. Quasi-two-dimensional electron (or hole) systems are the ones which admit generation of a spin current through spin-orbit coupling. In this paper, the question of gauge covariance in the non-Abelian gauge-field formulation of two space-dimensional systems with spin-orbit coupling relevant to spintronics is investigated. Although these are generally gauge-fixed models, it is found that, for the class of gauge fields that are space-time independent and satisfy a \(U(1)\) algebra, thus having a vanishing field strength, there is a residual gauge freedom in the Hamiltonian.