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Phys. Rev. B 80, 012401 (2009) [4 pages]

Conservation and persistence of spin currents and their relation to the Lieb-Schulz-Mattis twist operators

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N. Bray-Ali1 and Z. Nussinov2
1Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, USA
2Department of Physics, Washington University, St. Louis, Missouri 63160, USA

Received 6 March 2008; revised 21 April 2009; published 6 July 2009

Systems with spin-orbit coupling do not conserve “bare” spin current j. A recent proposal for a conserved spin current J [ J. Shi et al. Phys. Rev. Lett. 96 076604 (2006)] does not flow persistently in equilibrium. We suggest another conserved spin current J̅ that may flow persistently in equilibrium. We give two arguments for the instability of persistent current of the form J: one based on the equations of motions and another based on a variational construction using Lieb-Schulz-Mattis twist operators. In the absence of spin-orbit coupling, the three forms of spin current coincide.

© 2009 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.80.012401
DOI:
10.1103/PhysRevB.80.012401
PACS:
72.10.Bg, 72.20.Dp, 73.63.Hs