Observation of a supersolid stripe state in two-dimensional dipolar gases

TL;DR

This paper reports the first direct observation of a 2D supersolid stripe phase in a dipolar quantum gas, demonstrating its density modulation, phase coherence, and hydrodynamic properties, thus confirming long-standing theoretical predictions.

Contribution

It provides the first experimental evidence of a 2D supersolid in a dipolar gas, confirming theoretical models and revealing a new mechanism for supersolid formation in low dimensions.

Findings

Direct imaging of density modulation confirms supersolid stripe phase

Phase coherence demonstrated through matter-wave interference

Hydrodynamic behavior observed in collective excitations

Abstract

Fluctuations typically destroy long-range order in two-dimensional (2D) systems, posing a fundamental challenge to the existence of exotic states like supersolids, which paradoxically combine solid-like structure with frictionless superfluid flow. While long-predicted, the definitive observation of a 2D supersolid has remained an outstanding experimental goal. Here, we report the observation of a supersolid stripe phase in a strongly dipolar quantum gas of erbium atoms confined to 2D. We directly image the periodic density modulation, confirming its global phase coherence through matter-wave interference and demonstrating its phase rigidity relevant to the low-energy Goldstone mode, consistent with numerical calculations. Through collective excitation measurements, we demonstrate the hydrodynamic behavior of the supersolid. This work highlights a novel mechanism for supersolid formation in low dimensions, and opens the door for future research on the intricate interplay between temperature, supersolidity, and dimensionality.