Topological Insulators and Nematic Phases from Spontaneous Symmetry Breaking in 2D Fermi Systems with a Quadratic Band Crossing

Journal Article · Fri Jul 24 00:00:00 EDT 2009 · Physical Review Letters

DOI:https://doi.org/10.1103/PHYSREVLETT.103.046811· OSTI ID:21347093

Kai, Sun; Fradkin, Eduardo ^[1]; Hong, Yao; Kivelson, Steven A ^[2]

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1. Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080 (United States)
2. Department of Physics, Stanford University, Stanford, California 94305 (United States)

We investigate the stability of a quadratic band-crossing point (QBCP) in 2D fermionic systems. At the noninteracting level, we show that a QBCP exists and is topologically stable for a Berry flux +-2pi if the point symmetry group has either fourfold or sixfold rotational symmetries. This putative topologically stable free-fermion QBCP is marginally unstable to arbitrarily weak short-range repulsive interactions. We consider both spinless and spin-1/2 fermions. Four possible ordered states result: a quantum anomalous Hall phase, a quantum spin Hall phase, a nematic phase, and a nematic-spin-nematic phase.

• OSTI ID: 21347093
• Journal Information: Physical Review Letters, Vol. 103, Issue 4; Other Information: DOI: 10.1103/PhysRevLett.103.046811; (c) 2009 The American Physical Society; ISSN 0031-9007
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
FERMIONS
INTERACTIONS
SPIN
STABILITY
SYMMETRY
SYMMETRY BREAKING
SYMMETRY GROUPS
TOPOLOGY
ANGULAR MOMENTUM
MATHEMATICS
PARTICLE PROPERTIES