Paper on nematic quantum liquid crystals in frustrated lattices published in Phys. Rev. B

Guanyu-PRB2016The problem of interacting bosons in frustrated lattices is an intricate one due to the absence of a unique minimum in the single-particle dispersion where macroscopic number of bosons can condense. In this paper, we consider a family of tight-binding models with macroscopically degenerate lowest energy bands, separated from other bands by a gap.We predict the formation of exotic states that spontaneously break rotational symmetry at relatively low filling. These states belong to three nematic phases:Wigner crystal, supersolid, and superfluid. The Wigner crystal phase is established exactly at low filling. Supersolid and superfluid phases, at larger filling, are obtained by making use of a projection onto the flat band, construction of an appropriate Wannier basis, and subsequent mean-field treatment. The nematic superfluid that we predict is uniform in real space but has an anisotropic momentum distribution, providing a novel scenario for Bose condensation with an additional nematic order. Our findings open up a promising direction of studying microscopic quantum liquid crystalline phases of bosons.

Link: Phys. Rev. B 93, 144508 (2016)