Konwersatorium wydziałowe (online)

Dnia 2020-11-10 o godzinie 13:15 odbędzie się wykład (konwersatorium odbędzie się „online” z wykorzystaniem platformy ZOOM), na którym dr Krzysztof Gawryluk z Katedry Astrofizyki i Fizyki Teoretycznej wygłosi wykład pt:

„Berezinskii-Kosterlitz-Thouless phase„

Serdecznie zapraszamy

Andrzej Maziewski

Jerzy Przeszowski

 

Berezinskii-Kosterlitz-Thouless phase

Intrigued by a recent experiment [J.L. Ville et al., Phys. Rev. Lett.121, 145301 (2018)], we study the sound propagation in a two-dimensional weakly interacting uniform Bose gas. Using the classical fieldsapproximation we first successfully reproduce original experimental results and next, we analyze in detail the nature of generated density waves. Playing with a spatial resolution of our (numerical) imaging system, we identify observed structures as quasisolitons and uncover their internal complexity. Quasisolitons break into vortex pairs as time progresses, eventually reaching an equilibrium state. We find this state, characterized by only fluctuating in time averaged number of pairs of opposite charge vortices and by appearance of quasi-long-range  order, as the Berezinskii-Kosterlitz-Thouless (BKT) phase.