Berezinskii-Kosterlitz-Thouless Transition in Two-Dimensional Dipolar Stripes

TL;DR

This study investigates the Berezinskii-Kosterlitz-Thouless transition in a two-dimensional dipolar system, revealing how superfluidity and phase transitions depend on polarization angle and phase type using Monte Carlo simulations.

Contribution

It provides the first detailed Monte Carlo analysis of BKT transitions in anisotropic 2D dipolar systems with stripe phases.

Findings

Both phases follow BKT scaling laws.

Transition temperature decreases with increasing tilting angle.

Superfluidity varies with temperature and phase orientation.

Abstract

A two-dimensional quantum system of dipoles, with a polarization angle not perpendicular to the plane, shows a transition from a gas to a stripe phase. We have studied the thermal properties of these two phases using the path integral Monte Carlo (PIMC) method. By simulating the thermal density matrix, PIMC provides exact results for magnitudes of interest such as the superfluid fraction and the one-body density matrix. As it is well known, in two dimensions the superfluid-to-normal phase transition follows the Berezinskii-Kosterlitz-Thouless (BKT) scenario. Our results show that both the anisotropic gas and the stripe phases follow the BKT scaling laws. At fixed density and increasing the tilting angle, the transition temperature decreases in going from the gas to the stripe phase. Superfluidity in the perpendicular direction to the stripes is rather small close to the critical temperature but it becomes larger at lower temperatures, mainly close to the transition to the gas. Our results are in qualitative agreement with the supersolidity observed recently in a quasi-one-dimensional array of dipolar droplets.