Quantum phase transitions to superfluid state of chains in a polarized gas of dipolar molecules

TL;DR

This paper investigates quantum phase transitions to superfluid states in a layered gas of dipolar molecules, revealing different universality classes depending on inter-layer tunneling, using Monte Carlo simulations and conformal field theory analysis.

Contribution

It demonstrates how inter-layer tunneling alters the universality class of the quantum phase transition in layered dipolar molecular gases.

Findings

Transition without tunneling is BKT type in 1D density matrix

Inter-layer tunneling shifts transition to 2D Potts universality

Field theory descriptions align with simulation results

Abstract

We analyze the nature of quantum phase transition to a superfluid state of flexible chains in a gas of polar bosonic molecules confined in a stack of $N$ identical 1d ("cigar" type) optical lattice layers and polarized perpendicularly to the layers. Monte Carlo simulations within the $J$-current model show that, in the absence of the inter-tube tunneling, the transition to the $N$-layered superfluid is in the Berezinskii-Kosterlitz-Thouless universality class in the one-particle density matrix channel. The inter-layer tunneling changes it to the $q=N$ 2d Potts universality. The low energy field descriptions of the transition are discussed in terms of conformal field theories.