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Exact SU(2) symmetry and persistent spin helix in a spin-orbit coupled system
B Andrei Bernevig1, J Orenstein, Shou-Cheng Zhang
1Department of Physics, McCullough Building, Stanford University, Stanford, California 94305-4045, USA.
Physical Review Letters
|February 7, 2007
Summary
A novel SU(2) spin rotation symmetry in spin-orbit coupled systems leads to a persistent spin helix with an infinite spin lifetime. This robust symmetry is observable through suggested experimental methods.
Area of Science:
- Condensed matter physics
- Quantum mechanics
- Spintronics
Background:
- Spin-orbit coupling typically breaks spin rotation symmetry in materials.
- Understanding spin dynamics is crucial for developing advanced electronic devices.
Purpose of the Study:
- To discover and characterize a new SU(2) spin rotation symmetry in specific spin-orbit coupled systems.
- To investigate the implications of this symmetry on spin lifetime and dynamics.
- To propose experimental methods for observing the predicted phenomena.
Main Methods:
- Theoretical analysis of spin-orbit coupled models, specifically focusing on equal Rashba and Dresselhauss coupling and the [110] Dresselhauss model.
- Derivation of symmetry-generating operators and analysis of their wave vector dependence.
- Calculation of spin fluctuation dynamics at and away from the symmetry point.
Main Results:
- Discovery of a robust SU(2) spin rotation symmetry, resistant to spin-independent disorder and interactions.
- Identification of a specific wave vector where this symmetry leads to an infinite spin lifetime, forming a persistent spin helix.
- Characterization of spin fluctuation dynamics influenced by this novel symmetry.
Conclusions:
- The identified SU(2) symmetry offers a new perspective on spin dynamics in spin-orbit coupled systems.
- The persistent spin helix represents a unique quantum phenomenon with potential applications in spintronics.
- Experimental verification of the persistent spin helix is feasible and encouraged.
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