Observation of Self-Bound Droplets of Ultracold Dipolar Molecules

• URL: http://arxiv.org/abs/2507.15208v1
• Date: Mon, 21 Jul 2025 03:15:15 GMT
• Title: Observation of Self-Bound Droplets of Ultracold Dipolar Molecules
• Authors: Siwei Zhang, Weijun Yuan, Niccolò Bigagli, Haneul Kwak, Tijs Karman, Ian Stevenson, Sebastian Will,
• Abstract summary: We report the formation of self-bound droplets and droplet arrays in an ultracold gas of strongly dipolar sodium-cesium molecules.<n>The droplets exhibit densities up to 100 times higher than the initial BEC, reaching the strongly interacting regime.<n>This work establishes ultracold molecules as a system for the exploration of strongly dipolar quantum matter.
• Score: 2.686226765720665
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Ultracold gases of dipolar molecules have long been envisioned as a platform for the realization of novel quantum phases. Recent advances in collisional shielding, protecting molecules from inelastic losses, have enabled the creation of degenerate Fermi gases and, more recently, Bose-Einstein condensation of dipolar molecules. However, the observation of quantum phases in ultracold molecular gases that are driven by dipole-dipole interactions has so far remained elusive. In this work, we report the formation of self-bound droplets and droplet arrays in an ultracold gas of strongly dipolar sodium-cesium molecules. Starting from a molecular Bose-Einstein condensate (BEC), microwave dressing fields are used to induce dipole-dipole interactions with controllable strength and anisotropy. By varying the speed at which interactions are induced, covering a dynamic range of four orders of magnitude, we prepare droplets under equilibrium and non-equilibrium conditions, observing a transition from robust one-dimensional (1D) arrays to fluctuating two-dimensional (2D) structures. The droplets exhibit densities up to 100 times higher than the initial BEC, reaching the strongly interacting regime, and suggesting the possibility of a quantum-liquid or crystalline state. This work establishes ultracold molecules as a system for the exploration of strongly dipolar quantum matter and opens the door to the realization of self-organized crystal phases and dipolar spin liquids in optical lattices.

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