In-situ Observation of Magnetostriction Crossover in a Strongly Dipolar Two-Dimensional Bose Gas

Abstract

Magnetostriction, the anisotropic spatial deformation, is a hallmark of dipolar gases with strong long-range interactions, yet it poses a challenge for in-situ characterization. Here, we observe a magnetostriction crossover from the strongly anisotropic superfluid phase to the nearly isotropic normal phase using in-situ imaging of quasi-two-dimensional 166Er gases. Then, we develop a quasi-2D Hartree-Fock-mean-field framework that provides a robust tool for interaction-aware thermometry, enabling the determination of temperature and chemical potential across all dipole orientations from a single fit. We further demonstrate that the low-density wings effectively obey a local-density equation of state. Finally, we reveals the crossover from the isotropic thermal wings to the anisotropic coherent core in a single in-situ image, providing a pathway for future accurate studies of strongly dipolar superfluidity and thermodynamics in 2D.