Two-Dimensional Supersolid Formation in Dipolar Condensates

TL;DR

This paper demonstrates a practical method to create stable two-dimensional supersolids in dipolar condensates using evaporative cooling, bypassing instabilities and providing a pathway for large supersolid arrays.

Contribution

It develops a finite-temperature stochastic Gross-Pitaevskii model and experimentally shows a new evaporative cooling technique to produce stable 2D supersolids.

Findings

Evaporative cooling into the supersolid phase is effective in 2D.

The resulting supersolid is stable at nonzero temperature.

Experimental realization confirms the theoretical approach.

Abstract

Dipolar condensates have recently been coaxed to form the long-sought supersolid phase. While one-dimensional supersolids may be prepared by triggering a roton instability, we find that such a procedure in two dimensions (2D) leads to a loss of both global phase coherence and crystalline order. Unlike in 1D, the 2D roton modes have little in common with the supersolid configuration. We develop a finite-temperature stochastic Gross-Pitaevskii theory that includes beyond-mean-field effects to explore the formation process in 2D and find that evaporative cooling directly into the supersolid phase--hence bypassing the first-order roton instability--can produce a robust supersolid in a circular trap. Importantly, the resulting supersolid is stable at the final nonzero temperature. We then experimentally produce a 2D supersolid in a near-circular trap through such an evaporative procedure. Our work provides insight into the process of supersolid formation in 2D and defines a realistic path to the formation of large two-dimensional supersolid arrays.