Quantum phase transition of a two-dimensional quadrupolar system

TL;DR

This study investigates the quantum phase transition in a two-dimensional quadrupolar Bose system, revealing a transition from gas to solid phase with observable collective excitations, using diffusion Monte Carlo simulations.

Contribution

The paper provides the first detailed phase diagram of a 2D quadrupolar Bose system and predicts a quantum phase transition with specific measurable parameters.

Findings

Identified a quantum phase transition from gas to solid phase.

Measured the Lindemann ratio and condensate fraction at transition.

Observed strong rotonization near the phase transition.

Abstract

Ensembles with long-range interactions between particles are promising for revealing strong quantum collective effects and many-body phenomena. Here we study the ground-state phase diagram of a two-dimensional Bose system with quadrupolar interactions using a diffusion Monte Carlo technique. We predict a quantum phase transition from a gas to a solid phase. The Lindemann ratio and the condensate fraction at the transition point are $\gamma=0.269(4)$ and $n_0/n=0.031(4)$, correspondingly. We observe the strong rotonization of the collective excitation branch in the vicinity of the phase transition point. Our results can be probed using state-of-the-art experimental systems of various nature, such as quasi-two-dimensional systems of quadrupolar excitons in transition metal dichalcogenide (TMD) trilayers, quadrupolar molecules, and excitons or Rydberg atoms with quadrupole moments induced by strong magnetic fields.