title: Exact SU(2) symmetry and persistent spin helix in a spin-orbit coupled system.
abstract: Spin-orbit coupled systems generally break the spin rotation symmetry. However, for a model with equal Rashba and Dresselhauss coupling constants, and for the [110] Dresselhauss model, a new type of SU(2) spin rotation symmetry is discovered. This symmetry is robust against spin-independent disorder and interactions and is generated by operators whose wave vector depends on the coupling strength. It renders the spin lifetime infinite at this wave vector, giving rise to a persistent spin helix. We obtain the spin fluctuation dynamics at, and away from, the symmetry point and suggest experiments to observe the persistent spin helix.
authors.affiliation: Department of Physics, McCullough Building, Stanford University, Stanford, California 94305-4045, USA.
authors.forename: B Andrei
authors.initials: BA
authors.lastname: Bernevig
authors.forename: J
authors.initials: J
authors.lastname: Orenstein
authors.forename: Shou-Cheng
authors.initials: SC
authors.lastname: Zhang