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MO: Fachverband Molekülphysik

MO 22: Poster – Cold Molecules (joint session MO/Q)

MO 22.4: Poster

Mittwoch, 4. März 2026, 17:00–19:00, Philo 1. OG

Crystal-to-droplet melting in ultracold polar molecules — •William Freitas, Panagiotis Giannakeas, and Jan M Rost — Max Planck Institute for the Physics of Complex Systems, Dresden, Germany

Microwave-shielded polar molecules provide a novel platform for exploring dipolar matter in the strongly correlated regime, where dipole-dipole interactions naturally confine molecular ensembles to quasi-two-dimensional geometries. The competition between the long-range antidipolar attraction and the anisotropic short-range repulsion leads to a rich variety of phases, ranging from quantum droplets to crystalline structures.

In this work, we investigate the transition between the crystal and droplet phases, focusing specifically on the melting of crystalline order for finite systems. For systems of up to N = 40 molecules, we observe that the system develops droplet-ring configurations as an intermediate state between the droplet and crystal phases, characterized by a superfluid fraction below unity. Moreover, we show that the droplet-ring state retains six-fold symmetry, a fingerprint of the underlying crystal structure, as demonstrated by the pair-correlation function and structure factor.

Our simulations employ the Variational Monte Carlo method with a neural-network quantum state as the trial wave function. This approach provides a highly flexible functional form and enables stable energy minimization, yielding an accurate description of the ground state and an efficient treatment of strongly correlated finite systems.

Keywords: Ultracold polar molecules; Artificial neural networks; Variational Monte Carlo; Superfluidity