Scientific Results

Nonequilibrium Phase Transition in a Two-Dimensional Driven Open Quantum System

Year: 2015

Authors: Dagvadorj G., Fellows JM., Matyjaskiewicz S., Marchetti FM., Carusotto I., Szymanska MH.

Autors Affiliation: Univ Warwick, Dept Phys, Coventry CV4 7AL, W Midlands, England; Nomura Int Plc, Dept Risk Methodol, London EC4R 3AB, England;‎ Univ Autonoma Madrid, Dept Fis Teor Mat Condensada, E-28049 Madrid, Spain; Univ Autonoma Madrid, Condensed Matter Phys Ctr IFIMAC, E-28049 Madrid, Spain;‎ Univ Trento, INO CNR BEC Ctr, I-38123 Povo, Italy;Univ Trento, Dipartimento Fis, I-38123 Povo, Italy; UCL, Dept Phys & Astron, London WC1E 6BT, England

Abstract: The Berezinskii-Kosterlitz-Thouless mechanism, in which a phase transition is mediated by the proliferation of topological defects, governs the critical behavior of a wide range of equilibrium two-dimensional systems with a continuous symmetry, ranging from spin systems to superconducting thin films and two-dimensional Bose fluids, such as liquid helium and ultracold atoms. We show here that this phenomenon is not restricted to thermal equilibrium, rather it survives more generally in a dissipative highly nonequilibrium system driven into a steady state. By considering a quantum fluid of polaritons of an experimentally relevant size, in the so-called optical parametric oscillator regime, we demonstrate that it indeed undergoes a phase transition associated with a vortex binding-unbinding mechanism. Yet, the exponent of the power-law decay of the first-order correlation function in the (algebraically) ordered phase can exceed the equilibrium upper limit: this shows that the ordered phase of driven-dissipative systems can sustain a higher level of collective excitations before the order is destroyed by topological defects. Our work suggests that the macroscopic coherence phenomena, observed recently in interacting two-dimensional light-matter systems, result from a nonequilibrium phase transition of the Berezinskii-Kosterlitz-Thouless rather than the Bose-Einstein condensation type.


Volume: 5 (4)      Pages from: 041828-1  to: 041828-9


DOI: 10.1103/PhysRevX.5.041028

Citations: 53
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