Mainz 2026 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 40: Ultra-cold Atoms, Ions and BEC V (joint session A/Q)

A 40.3: Vortrag

Freitag, 6. März 2026, 11:45–12:00, N 1

Observation of a structural transition in dipolar (super)solids — •Karthik Chandrashekara, Jianshun Gao, Christian Gölzhäuser, Lily Platt, Wyatt Kirkby, Manon Ballu, and Lauriane Chomaz — Physikalisches Institut der Universität Heidelberg, Heidelberg, Germany

Spontaneous formation of spatially nonuniform, periodic structures from homogeneous backgrounds is well known in classical systems and has analogues in quantum matter, where interactions can generate such patterns even at equilibrium. Dipolar Bose gases provide a striking example: long-range, anisotropic dipole-dipole interactions stabilized by quantum fluctuations yield ordered crystalline phases that may remain superfluid, first observed in one-dimensional geometries and later in planar systems. For a planar dipolar Bose gas with transverse dipole orientation, extended mean-field theory predicts triangular droplet, stripe, and honeycomb-like structures. Transitions from unmodulated to these modulated states are generally first order except at a critical point allowing a continuous transition. Tilting the dipoles from the plane normal alters these boundaries, broadening the stripe region and introducing new critical points. Varying the scattering length can thus drive transitions to triangular droplet or stripe phases depending on the density and angle. Here, we experimentally explore the phase diagram of a dipolar gas in a surfboard-shaped trap using interaction ramps and control of dipole tilts. We observe the formation of crystalline phases, including a tilt-induced stripe-like (super)solid, and investigate the structural transitions between the morphologies.

Keywords: long-range interactions; dipolar BEC; supersolidity; phase transitions