Topological quantum phase transitions of attractive spinless fermions in a honeycomb lattice

• Published in: Europhysics letters Vol. 93; no. 3; p. 37008
• Main Authors: Poletti, D, Miniatura, C, Grémaud, B
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01-02-2011; EPS, SIF, EDP Sciences and IOP Publishing
• Subjects: 67.85.Lm; 74.20.-z; 74.20.Rp
• ISSN: 0295-5075; 1286-4854
• DOI: 10.1209/0295-5075/93/37008

We investigate a spinless Fermi gas trapped in a honeycomb optical lattice with attractive nearest-neighbor interactions. At zero temperature, the mean-field theory predicts three quantum phase transitions, two being topological. At low interactions, the system is semi-metallic. Increasing the interaction further, the semi-metal destabilizes into a fully gapped superfluid. At larger interactions, a topological transition occurs and this superfluid phase becomes gapless, with Dirac-like dispersion relations. Finally, increasing again the interaction, a second topological transition occurs and the gapless superfluid is replaced by a different fully gapped superfluid phase. We analyze these different quantum phases as the temperature and the lattice filling are varied.