Topological structures in spinor Bose-Einstein condensates

Seminar

Topological defects and textures provide intriguing conceptual links between many otherwise distant branches of physics. Spinor Bose–Einstein condensates (BECs) in dilute atomic gases are one of the most capable systems available for the study of topological structures due to the diverse range of broken symmetries associated with the different magnetic phases in the system. For example, spinor BECs can host vortices, which are analogous with hypothetical cosmic strings, and monopoles, which in turn can simulate Dirac's magnetic monopole. More complicated three-dimensional textures such as quantum knots can also be created in the condensate. In this talk I will present my PhD work on the topic at hand. I will start with a brief introduction to the physics of spinor BECs and continue with an outline on how we create topological structures in the lab. I will then discuss in more detail about our recent experimental observation of the decay dynamics of quantum knots [1]. In this study, we find that the knot gives rise to a rapid decay of the underlying magnetic phase, leading to the scrambling of magnetic and nonmagnetic domains in the condensate. Consequently, the knot quickly disappears, but over long evolution times we surprisingly find that the scrambled magnetic domains reorder into a spin vortex configuration with a nonmagnetic core. [1] "Decay of a quantum knot", T. Ollikainen, A. Blinova, M. Möttönen, and D. S. Hall, arXiv:1908.01285 (Phys. Rev. Lett. 123, 163003 (2019))

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