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Q: Fachverband Quantenoptik und Photonik
Q 43: Ultracold Matter (Bosons) III (joint session Q/A)
Q 43.6: Vortrag
Mittwoch, 12. März 2025, 15:45–16:00, WP-HS
Anomalous non-thermal fixed point in a quasi-2d dipolar Bose gas — •Niklas Rasch1, Wyatt Kirkby1,2, Lauriane Chomaz2, and Thomas Gasenzer1,3 — 1Kirchhoff-Institut für Physik, Universität Heidelberg, Im Neuenheimer Feld 227 — 2Physikalisches Institut, Universität Heidelberg, Im Neuenheimer Feld 226 — 3Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16
This work focuses on anomalous non-thermal fixed-points (NTFP) in the temporal evolution of a 2d dipolar Bose gas, exhibiting slow, subdiffusive coarsening characterized by algebraic growth of a characteristic length scale L(t)∼ tβ with β≪ 1/2. Sampling from various initial vortex configurations, we evolve the Bose gas using the semi-classical truncated-Wigner approach. For a highly dilute gas, anomalous scaling prevails, with an exponent β∼1/5, for various dipolar strengths and tilting angles. For late times or strong dissipation we observe the transition into diffusive scaling with β=1/2. In the quantum regime, realised for typical experimental parameters, we also find anomalously slow scaling, albeit with more fluctuations than in the classical limit. Within a quasi-2d setting, we analyze the dependence of the scaling exponents on the anisotropic and long-range nature of the dipolar interaction. Further, we investigate the role of vortex (anti-)clustering and find both strong clustering as well as anti-clustering throughout the anomalous scaling regime. Our results support the universal nature of the anomalous NTFP and hint towards three-vortex collisions as the primary source for the subdiffusive coarsening.
Keywords: Non-Thermal Fixed Points; Dipolar gases; non-equilibrium; scaling; vortices