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An Exact SU(2) Symmetry and Persistent Spin Helix in a Spin-Orbit Coupled System

B. Andrei Bernevig·J. Orenstein·Shou-Cheng Zhang
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Abstract

Spin-orbit coupled systems generally break the spin rotation symmetry. However, for a model with equal Rashba and Dresselhauss coupling constant (the ReD model), 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 wavevector depends on the coupling strength. It renders the spin lifetime infinite at this wavevector, giving rise to a Persistent Spin Helix (PSH). We obtain the spin fluctuation dynamics at, and away, from the symmetry point, and suggest experiments to observe the PSH.

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B. Andrei Bernevig, J. Orenstein, Shou-Cheng Zhang. 2006-06-07. An Exact SU(2) Symmetry and Persistent Spin Helix in a Spin-Orbit Coupled System. https://doi.org/10.1103/physrevlett.97.236601

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