Volume 93, Number 3, February 2011
|Number of page(s)||6|
|Section||Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties|
|Published online||17 February 2011|
Topological quantum phase transitions of attractive spinless fermions in a honeycomb lattice
Centre for Quantum Technologies, National University of Singapore - 3 Science Drive 2, Singapore 117543, Singapore
2 Centre de Physique Théorique, Ecole Polytechnique, CNRS - 91128 Palaiseau Cedex, France, EU
3 Département de Physique Théorique, Université de Genève - 24 quai Ansermet, CH-1211 Genève, Switzerland
4 Institut Non Linéaire de Nice, UMR 6618, UNS, CNRS - 1361, route des Lucioles, 06560 Valbonne, France, EU
5 Department of Physics, National University of Singapore - 2 Science Drive 3, Singapore 117542, Singapore
6 Laboratoire Kastler-Brossel, Ecole Normale Supérieure, CNRS, UPMC - 4, place Jussieu, 75005 Paris, France, EU
Accepted: 19 January 2011
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.
PACS: 74.20.-z – Theories and models of superconducting state / 74.20.Rp – Pairing symmetries (other than s-wave) / 67.85.Lm – Degenerate Fermi gases
© EPLA, 2011
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