Metallic state in bosonic systems with continuously degenerate minima

Abstract

In systems above one dimension a continuously degenerate minimum of the single particle dispersion is realized due to one or a combination of system-parameters such as lattice structure, isotropic spin-orbit coupling, and interactions. A unit codimension of the dispersion-minima leads to a divergent density of states which enhances the effects of interactions, and may lead to novel states of matter as exemplified by Luttinger liquids in one dimensional bosonic systems. Here we show that in dilute, homogeneous bosonic systems above one dimension, weak, spin-independent, inter-particle interactions stabilize a metallic state at zero temperature in the presence of a curved manifold of dispersion minima. In this metallic phase the system possesses a quasi long-range order with non-universal scaling exponents. At a fixed positive curvature of the manifold, increasing either the dilution or the interaction strength destabilizes the metallic state towards charge density wave states that break one or more symmetries. The magnitude of the wave vector of the dominant charge density wave state is controlled by the product of the mean density of bosons and the curvature of the manifold. We obtain the zero temperature phase diagram, and identify the phase boundary.