Tuning across Universalities with a Driven Open Condensate

Abstract

Driven-dissipative systems in two dimensions can differ substantially from their equilibrium counterparts. In particular, a dramatic loss of off-diagonal algebraic order and superfluidity has been predicted to occur because of the interplay between coherent dynamics and external drive and dissipation in the thermodynamic limit. We show here that the order adopted by the system can be substantially altered by a simple, experimentally viable tuning of the driving process. More precisely, by considering the longwavelength phase dynamics of a polariton quantum fluid in the optical parametric oscillator regime, we demonstrate that simply changing the strength of the pumping mechanism in an appropriate parameter range can substantially alter the level of effective spatial anisotropy induced by the driving laser and move the system into distinct scaling regimes. These include (i) the classic algebraically ordered superfluid below the Berezinskii-Kosterlitz-Thouless (BKT) transition, as in equilibrium; (ii) the nonequilibrium, longwavelength-fluctuation-dominated Kardar-Parisi-Zhang (KPZ) phase; and the two associated topologicaldefect-dominated disordered phases caused by proliferation of (iii) entropic BKT vortex-antivortex pairs or (iv) repelling vortices in the KPZ phase. Furthermore, by analyzing the renormalization group flow in a finite system, we examine the length scales associated with these phases and assess their observability in current experimental conditions.

Topological Defects in Anisotropic Driven Open Systems

“…Consequently, the characteristic KT behavior such as an essential singularity of the correlation length and an universal jump (rounded by finite size) of the superfluid density gives way to novel universal behavior. This prediction could be checked directly in experiments (e.g., with exciton-polaritons, see [18] for relevant parameter regimes) or numerics [37]. The modification of the vortex interaction should also have directly observable effects on phase-ordering kinetics [38][39][40][41], which is an in-teresting problem for further studies.…”

“…Due to this non-linear term, the vortex interaction is exponentially screened at large distances -thus, the ordered phase ceases to exist. This finding is particularly relevant, since the cKPZ equation is the long-wavelength description of a vast variety of systems, ranging from "polar active smectics" or "moving stripes" [11], to driven-dissipative condensates such as exciton-polaritons [3,[8][9][10][12][13][14][15][16][17][18][19], synchronization in arrays of limit-cycle oscillators [20], and limit-cycle phases that emerge from a Hopf bifurcation [21][22][23][24][25] such phases have attracted a lot of attention recently and could be coined dissipative time crystals [26].…”

“…Conclusions.-We studied the effect of strong spatial anisotropy on the structure and dynamics of vortices in 2D out-of-equilibrium systems with U(1) symmetry. These are described by the caKPZ equation (1), and physical realizations include active systems [11], drivendissipative condensates [3,[8][9][10][12][13][14][15][16][17][18], oscillator arrays [20], and limit-cycle phases [21][22][23][24][25]. To address the thermodynamic stability of the ordered phase in which vortices exist only as tightly bound pairs, we considered the structure of single vortices.…”

Tuning the order of the nonequilibrium quantum phase transition in a hybrid atom-optomechanical system

“…Yet, from an experimental point of view, it is not easy to realize and control systems with a nonequilibrium phase transition, in particular when quantum fluctuations dominate over thermal effects from the environment. Currently discussed systems, which show nonequilibrium quantum phase transitions (NQPTs), are ultracold atoms in a lattice inside an optical cavity [4][5][6][7][8] and microcavity-polariton systems [9][10][11]. Laser-driving offers the unique possibility to address and switch between different phases of quantum many-body systems by tuning the pump strength.…”

Kibble-Zurek Mechanism in Driven Dissipative Systems Crossing a Nonequilibrium Phase Transition

“…Polaritons therefore constitute excellent physical platforms to explore the influence that the nonconservation of energy and particle number, and the breaking of the detailed balance condition, may have on the critical dynamics. Pioneering works have started addressing the new features exhibited by the ordered state [35,36], by the nonequilibrium phase transition [37][38][39][40], the extension of the adiabaticity concept to nonequilibrium scenarios [41][42][43], the spontaneous formation of defects under a time-dependent pump [44][45][46], and the late-time relaxation past a sudden quench [47,48].…”