Strongly anomalous non-thermal fixed point in a quenched two-dimensional Bose gas. (20th September 2017)

• Record Type: Journal Article
• Authors: Karl, Markus; Gasenzer, Thomas
• Is Part Of: New journal of physics. Volume 19:Number 9(2017:Sep.)
• Publication Date: 2017-09-20
• Subjects: supefluid turbulence -- nonthermal fixed points -- non-equilibrium scaling -- quench dynamics; 11.10.Wx -- 03.75.Lm -- 47.27.E- -- 67.85.De; Physics -- Periodicals; Physics; Periodicals; 530.05
• DOI: 10.1088/1367-2630/aa7eeb
• Languages: English
• ISSNs: 1367-2630

Abstract

Abstract: Universal scaling behavior in the relaxation dynamics of an isolated two-dimensional Bose gas is studied by means of semi-classical stochastic simulations of the Gross–Pitaevskii model. The system is quenched far out of equilibrium by imprinting vortex defects into an otherwise phase-coherent condensate. A strongly anomalous non-thermal fixed point is identified, associated with a slowed decay of the defects in the case that the dissipative coupling to the thermal background noise is suppressed. At this fixed point, a large anomalous exponent η ≃ − 3 and, related to this, a large dynamical exponent z ≃ 5 are identified. The corresponding power-law decay is found to be consistent with three-vortex-collision induced loss. The article discusses these aspects of non-thermal fixed points in the context of phase-ordering kinetics and coarsening dynamics, thus relating phenomenological and analytical approaches to classifying far-from-equilibrium scaling dynamics with each other. In particular, a close connection between the anomalous scaling exponent η, introduced in a quantum-field theoretic approach, and conservation-law induced scaling in classical phase-ordering kinetics is revealed. Moreover, the relation to superfluid turbulence as well as to driven stationary systems is discussed.