Mainz 2026 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 26: Poster – Ultracold Matter (joint session Q/A)

A 26.30: Poster

Mittwoch, 4. März 2026, 17:00–19:00, Philo 2. OG

Active magnetic field stabilization for a dipolar quantum gas experiment — •Tim Jeglortz, Paul Uerlings, Fiona Hellstern, Kevin Ng, Michael Wischert, Stephan Welte, Ralf Klemt, and Tilman Pfau — 5. Physikalisches Institut and Center for Integrated Quantum Science and Technology (IQST), Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany

We aim to experimentally investigate the fundamental low-lying excitations of a dipolar quantum gas of dysprosium atoms in a toroidal trap. In particular, we focus on the emergence of the Higgs amplitude mode across the transition from a superfluid to a supersolid as an indicator of spontaneous symmetry breaking. Precise control of the magnetic field is crucial, as the excitation energy close to the critical point in the phase diagram has a steep dependence on the relative dipolar interaction strength, serving as the control parameter, which is in turn set by a magnetic offset field in the vicinity of a Feshbach resonance. This necessitates sub-mG magnetic field stability.

This poster presents a solution for an active magnetic field stabilization setup that allows to attenuate fluctuations relative to an arbitrary offset magnetic field using an array of fluxgate sensors placed outside the science chamber. A digital stabilization loop that runs on a fast microcontroller including high-resolution analog-to-digital and digital-to-analog converters in combination with a dedicated set of field coils allows to infer and control the magnetic field at the site of the atoms and reduce the background noise, particularly power line noise at 50 Hz, up to a bandwidth of 1 kHz.

Keywords: magnetic field stabilization; dysprosium; BEC; dipolar; ultracold