title: Spontaneous time-reversal symmetry breaking for spinless fermions on a triangular lattice.
abstract: As a minimal fermionic model with kinetic frustration, we study a system of spinless fermions in the lowest band of a triangular lattice with nearest-neighbor repulsion. We find that the combination of interactions and kinetic frustration leads to spontaneous symmetry breaking in various ways. Time-reversal symmetry can be broken by two types of loop current patterns, a chiral one and one that breaks the translational lattice symmetry. Moreover, the translational symmetry can also be broken by a density wave forming a kagome pattern or by a Peierls-type trimerization characterized by enhanced correlations among the sites of certain triangular plaquettes (giving a plaquette-centered density wave). We map out the phase diagram as it results from leading-order Ginzburg-Landau mean-field theory. Several experimental realizations of the type of system under study are possible with ultracold atoms in optical lattices.
authors.affiliation: ICFO-Institut de Ciències Fotòniques, Parc Mediterrani de la Tecnologia, E-08860 Castelldefels, Spain.
authors.forename: O
authors.initials: O
authors.lastname: Tieleman
authors.forename: O
authors.initials: O
authors.lastname: Dutta
authors.forename: M
authors.initials: M
authors.lastname: Lewenstein
authors.forename: A
authors.initials: A
authors.lastname: Eckardt