Critical behavior of a chiral superfluid in a bipartite square lattice

TL;DR

This paper investigates the critical behavior of Bose-Einstein condensation in a bipartite square lattice, revealing a distinct universality class and the stabilization of chiral superfluid order through renormalization group analysis.

Contribution

It introduces a field theoretical model for a two-component Bose gas in a bipartite lattice, identifying a new universality class due to Umklapp scattering effects.

Findings

Chiral superfluid order is stabilized at low temperatures.

The phase transition is predicted to be first order.

The system belongs to a different universality class than in frustrated triangular lattices.

Abstract

We study the critical behavior of Bose-Einstein condensation in the second band of a bipartite optical square lattice in a renormalization group framework at one-loop order. Within our field theoretical representation of the system, we approximate the system as a two-component Bose gas in three dimensions. We demonstrate that the system is in a different universality class than the previously studied condensation in a frustrated triangular lattice due to an additional Umklapp scattering term, which stabilizes the chiral superfluid order at low temperatures. We derive the renormalization group flow of the system and show that this order persists in the low energy limit. Furthermore, the renormalization flow suggests that the phase transition from the thermal phase to the chiral superfluid state is first order.