Hexatic, Wigner Crystal, and Superfluid Phases of Dipolar Bosons

TL;DR

This paper maps out the finite temperature phase diagram of two-dimensional dipolar bosons, identifying various phases including superfluid, crystal, hexatic, and normal fluid, and discusses their stability and experimental detection methods.

Contribution

It introduces a comprehensive phase diagram for 2D dipolar bosons, highlighting the existence and stability of novel phases like dipolar hexatic fluid and metastable supersolid states.

Findings

DWC exists at low temperatures for high densities or strong interactions.

DHF phase appears at higher temperatures after melting DWC.

Stable phases can be distinguished via optical Bragg scattering.

Abstract

The finite temperature phase diagram of two-dimensional dipolar bosons versus dipolar interaction strength is discussed. We identify the stable phases as dipolar superfluid (DSF), dipolar Wigner crystal (DWC), dipolar hexatic fluid (DHF), and dipolar normal fluid (DNF). We also show that other interesting phases like dipolar supersolid (DSS) and dipolar hexatic superfluid (DHSF) are at least metastable, and can potentially be reached by thermal quenching. In particular, for large densities or strong dipolar interactions, we find that the DWC exists at low temperatures, but melts into a DHF at higher temperatures, where translational crystaline order is destroyed but orientational order is preserved. Upon further increase in temperature the DHF phase melts into the DNF, where both orientational and translational lattice order are absent. Lastly, we discuss the static structure factor for some of the stable phases and show that they can be identified via optical Bragg scattering measurements.