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TT: Fachverband Tiefe Temperaturen

TT 63: Low-Dimensional Systems: 2D - Theory

TT 63.12: Vortrag

Donnerstag, 10. März 2016, 12:30–12:45, H21

Spontaneous breaking of particle-hole-symmetry on a Lieb-lattice — •Johannes S. Hofmann¹, Thomas C. Lang^2,1, Martin Bercx¹, and Fakher F. Assaad¹ — ¹Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Germany — ²Institute for Theoretical Physics, University of Innsbruck, Austria

We study the t-V-model of spinless fermions on a two dimensional Lieb-lattice at half filling, using both exact diagonalization and continuous-time Quantum Monte Carlo (QMC) methods. The non-interacting model supports a Dirac cone as well as a flat band at the Fermi level. While the flatness is protected by the sub-lattice symmetry, a flat band is also highly susceptible to interaction effects. We find that nearest neighbor Coulomb repulsion leads to spontaneous breaking of the sub-lattice symmetry due to the formation of a charge density wave. In principle, this allows to further investigate the model away from half filling without introducing a sign problem to the QMC. We analyze the critical temperature of the phase transition and study its dependence on the interaction strength.