Group seminar at LMU and Zoom: Nonequilibrium spin dynamics in a strongly ferromagnetic spinor Bose-Einstein condensate

July 18, 2023

SeungJung Huh, Department of Physics at KAIST, South Korea
Group seminar at LMU seminar room and Zoom
Tuesday, July 18th, 09:00 am (MEZ)


In this talk, I will introduce our experiments on nonequilibrium spin dynamics in strongly ferromagnetic spinor Bose-Einstein condensates (BECs). In the first part, I will present the universal dynamics in a quenched ferromagnetic spin-1 condensate and the classification of the coarsening dynamics into a well-defined universality class [1]. After preparing an unmagnetized condensate in a two-dimensional harmonic trap, the spinor condensate is quenched to a ferromagnetic phase via microwave dressing. Analyzing the spin correlation function, we observe the dynamical scaling behavior characterized by scaling exponents, close to 0.58(2) and 0.43(2) for the dynamics in the easy-axis ferromagnetic phase and the isotropic ferromagnetic phase, respectively [2-3]. By investigating the symmetry of the order parameter and the dynamics of the topological defects, we can determine the universality class of the coarsening dynamics. In the second part, we explore the dynamical generation of a skyrmion spin texture by imprinting a spin current onto a single magnetic domain wall in the easy-axis ferromagnetic phase [4]. When the spin current exceeds a critical value, a quantum Kelvin-Helmholtz instability generates a flutter-finger pattern of domain wall waves. This instability can lead to the formation of skyrmion spin textures, where isolated spin up (down) domains are  immersed in the background of spin down (up) domains. By utilizing matter-wave interference techniques, we observe a fork-shaped interference pattern at the center of the isolated spin domain.

[1] SeungJung Huh, Koushik Mukherjee, Kiryang Kwon, Jihoon Seo, Junhyeok Hur, Simeon I. Mistakidis, H.R. Sadeghpour, and Jae-yoon Choi, arXiv:2303.05230v1 (2023).

[2] L. A. Williamson and P. B. Blakie, Phys. Rev. Lett 116, 025301 (2016).

[3] L. A. Williamson and P. B. Blakie, Phys. Rev. Lett 119, 255301 (2017).

[4] H. Takeuchi, Phys. Rev. A 105, 013328 (2022).


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