Berezinskii-Kosterlitz-Thouless phase induced by dissipating quasisolitons

TL;DR

This paper investigates sound propagation in a 2D Bose gas, revealing how strong perturbations lead to quasisolitons that evolve into vortex pairs, culminating in a BKT phase with quasi-long-range order.

Contribution

It demonstrates the emergence of a BKT phase induced by dissipating quasisolitons in a 2D Bose gas, linking nonlinear excitations to topological phase transitions.

Findings

Identification of quasisolitons breaking into vortex pairs

Observation of a BKT phase with quasi-long-range order

Analysis of density wave behavior under different perturbation regimes

Abstract

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.