QFS 2016 Book of Abstracts

Abstracts

I4.4 Dynamics of half-quantum vortices in a spinor Bose-Einstein condensate Y. Shin(1,2), S. W. Seo(1) 1) Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea 2) Center for Correlated Electron Systems, Institute for Basic Science, Seoul 08826, Korea Quantum vortices with half the quantum circulation, known as half-quantum vortices (HQVs), have been observed in various spinor superfluid systems recently. In this presentation, we describe our recent experimental studies of HQV dynamics in a spin-1 antiferromagnetic Bose-Einstein condensate, where we observe the spontaneous dissociation of a singly charged vortex into a pair of HQVs and the collisional dynamics of HQV pairs, revealing the short range interactions arising from their ferromagnetic cores. Additionally, we investigate the relaxation dynamics of turbulent superflow containing many HQVs to find that spin waves are generated by the collisional motions of the HQVs. O4.7 Quantized vortices following reconnections Fonda Enrico(1), Sreenivasan Katepalli R.(2), Lathrop Daniel P.(3) 1) New York University, Physics Department, New York , New York 10012, USA 2) New York University, Departments of Physics and Mechanical Engineering and the Courant Institute of Mathematical Sciences, New York , New York 10012, USA 3) University of Maryland, Department of Physics, Department of Geology, Institute for Research in Electronics and Applied Physics, and Center for Nanophysics and Advanced Materials, College Park, Maryland 20742, USA We visualized quantized vortex reconnections in superfluid 4 He using sub-micron frozen air tracers. Compared to previous work, the fluid was almost at rest leading to fewer, straighter, slower-moving vortices. This condition allowed us to observe the propagation of Kelvin waves and to characterize the influence of the inter-vortex angle on the evolution of the recoiling vortices. The agreement of the experimental data to the analytical and numerical models suggests that the dynamics of the reconnection of long straight vortices on the scale of these experiments can be described by the self-similar solutions of the local induction approximation or Biot-Savart equations.

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