Regensburg 2013 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 50: Poster II

MA 50.77: Poster

Freitag, 15. März 2013, 10:30–13:30, Poster D

Ground state, static vortices, and dynamic excitations in magnon Bose-Einstein condensates — •Patryk Nowik-Boltyk¹, Oleksandr Dzyapko¹, Vladislav Demidov¹, Natasha Berloff², and Sergej O. Demokritov¹ — ¹Universität Münster; Institut für Angewandte Physik — ²University of Cambridge, Department of Applied Mathematics and Theoretical Physics

Although the basic properties of magnon Bose-Einstein condensates have been extensively studied during the last 5 years, details of the ground state, topological defects and induced dynamics of the condensate have not been addressed so far. Here we present a detailed study of the ground state of the condensate and static vortices as well as the dynamics of the condensate by means of space- and time-resolved Brillouin Light Scattering spectroscopy. We show that the intrinsic degeneracy of the condensate results in formation of a non-uniform ground state demonstrating a standing-wave of the condensate density. We also experimentally observed static defects in the condensate in a form of quantized vortices. The study of induced dynamics was performed using spatially and temporary non uniform external magnetic fields. For relatively slow field pulses we observe a quasi-adiabatical accommodation of the condensate density at the place of the field. If we use very short and fast field pulses, travelling density waves can be observed. If the field is varied periodically in the megahertz frequency range, traveling density waves are also observed. The dispersion relation of the newly observed waves is determined.