期刊
PHYSICAL REVIEW LETTERS
卷 103, 期 4, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevLett.103.046811
关键词
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资金
- National Science Foundation [DMR 0758462]
- Office of Science
- U.S. Department of Energy [DE-FG02-91ER45439]
- Frederick Seitz Materials Research Laboratory at the University of Illinois
- Gaballe Laboratory of Advanced Materials of Stanford University [FG02-06ER46287]
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [0758462] Funding Source: National Science Foundation
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 +/- 2 pi 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.
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