Mainz 2026 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 42: Poster – Ultracold Matter (joint session Q/A)

Q 42.9: Poster

Wednesday, March 4, 2026, 17:00–19:00, Philo 2. OG

Sine-Gordon solitons in a spinor Bose-Einstein condensate — •Florian Schmitt, Ido Siovitz, Yannick Deller, Alexander Schmutz, Raphael Schäfer, Alexander Flamm, Helmut Strobel, Markus K. Oberthaler, and Thomas Gasenzer — Kirchhoff- Institut für Physik, Universität Heidelberg, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany

This contribution is concerned with the theoretical analysis of topological defects in a Bose gas governed by the spin-1 Gross-Pitaveskii equation (GPE). We find that for a spinor gas consisting of Rubidium-87 atoms a local imprint in the spinor phase leads to a stable topological defect both in experiment and numerical time evolution. It exhibits key features of a kink solution of the sine-Gordon model, and we can calculate its velocity depending on the quadratic Zeeman shift from the spin-1 GPE Lagrangian as well as from its corresponding effective sine-Gordon theory. We investigate dynamics of kink collisions with respect to the observables of the spin-1 gas and are able to relate this defect living at low spin interaction strength to the exactly solvable regime of the spin-1 GPE Lagrangian.

Keywords: Superfluid; Solitons; Spinor; Non-equilibrium; Numerics