Topological insulators and nematic phases from spontaneous symmetry breaking in 2D fermi systems with a quadratic band crossing

Kai Sun, Hong Yao, Eduardo Fradkin, Steven A. Kivelson

Research output: Contribution to journalArticlepeer-review

Abstract

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 ±2π 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.

Original languageEnglish (US)
Article number046811
JournalPhysical review letters
Volume103
Issue number4
DOIs
StatePublished - Aug 6 2009

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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