$su(2)$ symmetry of XX spin chains

Abstract

We show that, after suitably adjusting a uniform transverse magnetic field, the generic inhomogeneous open XX spin chain has a two-fold degeneracy, and an exact $su(2)$ symmetry whose "inhomogeneous" nonlocal generators depend on coefficients that can be explicitly computed for models associated with discrete orthogonal polynomials.

arXiv comment7 pages; v2: references added; v3: more references added

References in corpus (9)

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• Long coherence times for edge spins
• Free-Fermion entanglement and orthogonal polynomials
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• Inhomogeneous XX spin chains and quasi-exactly solvable models
• Symmetry protected phases in inhomogeneous spin chains
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