Berezinskii-Kosterlitz-Thouless phase induced by dissipating quasisolitons

We theoretically study the sound propagation in a two-dimensional weakly interacting uniform Bose gas. Using the classical fields approximation we analyze in detail the properties of density waves generated both in a weak and strong perturbation regimes. While in the former case density excitations can be described in terms of hydrodynamic or collisionless sound, the strong disturbance of the system results in a qualitatively different response. We identify observed structures as quasisolitons and uncover their internal complexity for strong perturbation case. For this regime 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 a quasi-long-range order, as the Berezinskii-Kosterlitz-Thouless (BKT) phase.

Automated summary

In this study, the sound propagation in a two-dimensional weakly interacting uniform Bose gas is theoretically explored using classical fields approximation. Density waves generated in both weak and strong perturbation regimes are analyzed, with strong disturbances resulting in a qualitatively different response, identified as quasisolitons. In the strong perturbation regime, quasisolitons break into vortex pairs over time, eventually reaching an equilibrium state characterized by fluctuating in time averaged number of pairs of opposite charge vortices and quasi-long-range order, known as the Berezinskii-Kosterlitz-Thouless (BKT) phase.