Thermal and quantum fluctuations in chains of ultracold polar molecules

TL;DR

This paper investigates how thermal and quantum fluctuations influence the structural phase transition from linear to zigzag chains in ultracold polar molecules, using Monte Carlo simulations to analyze their effects.

Contribution

It provides a comparative analysis of thermal and quantum effects on self-organized molecular chains, highlighting their impact on structural phase transitions.

Findings

Pair correlation and structure factor reveal crystalline or liquid behavior.

Quantum fluctuations modify the critical density for the phase transition.

Experimental regimes where quantum effects are observable are identified.

Abstract

Ultracold polar molecules, in highly anisotropic traps and interacting via a repulsive dipolar potential, may form one-dimensional chains at high densities. According to classical theory, at low temperatures there exists a critical value of the density at which a second order phase transition from a linear to a zigzag chain occurs. We study the effect of thermal and quantum fluctuations on these self-organized structures using classical and quantum Monte Carlo methods, by means of which we evaluate the pair correlation function and the static structure factor. Depending on the parameters, these functions exhibit properties typical of a crystalline or of a liquid system. We compare the thermal and the quantum results, identifying analogies and differences. Finally, we discuss experimental parameter regimes where the effects of quantum fluctuations on the linear - zigzag transition can be observed.