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

Dagvadorj, Galbadrakh; Fellows, J. M.; Matyjaśkiewicz, S.; Marchetti, F. M.; Carusotto, Iacopo; Szymańska, M. H.

doi:10.1103/physrevx.5.041028

Cited by 103 publications

(164 citation statements)

References 42 publications

(63 reference statements)

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“…Thus, approaching the transition from above by lowering the pump power, the critical value x KT is reached first, and the system loses algebraic order through unbinding of vortices [300][301][302]. On the other hand, the crossover to the disordered regime will be controlled by KPZ physics once x * ≥ x KT , which can be achieved by increasing the loss rate (i.e., reducing the cavity Q) toγ ≈ 0.5.…”

Section: Absence Of Algebraic Order In 2dmentioning

confidence: 99%

Keldysh field theory for driven open quantum systems

2016

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Recent experimental developments in diverse areas -ranging from cold atomic gases to light-driven semiconductors to microcavity arrays -move systems into the focus which are located on the interface of quantum optics, many-body physics and statistical mechanics. They share in common that coherent and driven-dissipative quantum dynamics occur on an equal footing, creating genuine non-equilibrium scenarios without immediate counterpart in equilibrium condensed matter physics. This concerns both their non-thermal stationary states, as well as their many-body time evolution. It is a challenge to theory to identify novel instances of universal emergent macroscopic phenomena, which are tied unambiguously and in an observable way to the microscopic drive conditions. In this review, we discuss some recent results in this direction. Moreover, we provide a systematic introduction to the open system Keldysh functional integral approach, which is the proper technical tool to accomplish a merger of quantum optics and many-body physics, and leverages the power of modern quantum field theory to driven open quantum systems. CONTENTS

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Section: Absence Of Algebraic Order In 2dmentioning

confidence: 99%

Keldysh field theory for driven open quantum systems

2016

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“…We proposed an LCA prescription which can be further developed by considering these other mode spectra. An improved understanding of correlations in inhomogeneous systems is also mandatory for conducting experiments on universality in disordered systems [47][48][49] and situations far from equilibrium [50][51][52]. …”

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confidence: 99%

Quasi-long-range order in trapped two-dimensional Bose gases

Boettcher

Holzmann

2016

Phys. Rev. A

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We study the fate of algebraic decay of correlations in a harmonically trapped two-dimensional degenerate Bose gas. The analysis is inspired by recent experiments on ultracold atoms where power-law correlations have been observed despite the presence of the external potential. We generalize the spin wave description of phase fluctuations to the trapped case and obtain an analytical expression for the one-body density matrix within this approximation. We show that algebraic decay of the central correlation function persists to lengths of about 20% of the Thomas-Fermi radius. We establish that the trap-averaged correlation function decays algebraically with a strictly larger exponent weakly changing with trap size and find indications that the recently observed enhanced scaling exponents receive significant contributions from the normal component of the gas. We discuss radial and angular correlations and propose a local correlation approximation which captures the correlations very well. Our analysis goes beyond the usual local density approximation and the developed summation techniques constitute a powerful tool to investigate correlations in inhomogeneous systems.PACS numbers: 05.70. Jk, 64.60.an, With the achievement of quantum degeneracy in ultracold atom gases a new experimental platform for studying fundamental questions related to phase transitions and critical phenomena has appeared. In particular, correlation functions can be measured through interference and time-of-flight techniques [1][2][3][4][5][6][7]. A crucial aspect of the experiments, however, consists in the absence of translation invariance due to the presence of the external trapping potential. Consequently, correlations between points r and r are not uniquely determined by the value of r − r . This effect should be unimportant for short-range correlations, and, in fact, thermodynamic properties of ultracold gases are often very well-captured by a local density approximation. The situation changes drastically for a system at a critical point, where the correlation length diverges and thus competes with the inhomogeneity of the trapping potential.Whereas the experimental preparation of critical systems typically requires a highly fine-tuned setup, they are rather effortlessly realized in two-dimensional (2D) systems whose low-energy excitations can be mapped onto an XY model. Examples apart from 2D ultracold quantum gases [8][9][10][11][12] are given by thin Helium films [13], layered magnets [14,15], and 2D excitonpolariton condensates [16]. To quantify correlations in these systems we introduce the one-body density matrix ρ(r, r ) = Φ † (r)Φ(r ) , whereΦ † (r) is the creation operator for a particle at point r. For the spatially homogeneous case we then have ρ hom (r, r ) = f (|r − r |) with some function f (r) due to translation and rotation invariance. The Mermin-Wagner-Hohenberg theorem [17,18] forbids long-range order at any finite temperature such that lim r→∞ f (r) = 0. However, in the XY model an ordered low-temperature phase with inf...

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“…At equilibrium, it is of the BKT type in two dimensions, with a characteristic jump in the superfluid fraction. Indications that the BKT character of the phase transition is preserved out of equilibrium were found recently in numerical simulations in the parametric oscillation regime 25 , but the behavior of the normal and superfluid fractions has not been addressed yet.…”

Section: Discussionmentioning

confidence: 95%

Normal and superfluid fractions of inhomogeneous nonequilibrium quantum fluids

Gladilin

Wouters

2016

Phys. Rev. B

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We present a theoretical analysis of the normal and superfluid fractions of quantum fluids described by a nonequilibrium extension of the Gross-Pitaevskii equation in the presence of an external potential. Both disordered and regular potentials are considered. The normal and superfluid fractions are defined by the response of the nonequilibrium quantum fluid to a vector potential, in analogy with the equilibrium case. We find that the physical meaning of these definitions breaks down out of equilibrium. The normal and superfluid fractions no longer add up to one and for some types of external potentials, they can even become negative.

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

Cited by 103 publications

References 42 publications

Keldysh field theory for driven open quantum systems

Keldysh field theory for driven open quantum systems

Quasi-long-range order in trapped two-dimensional Bose gases

Normal and superfluid fractions of inhomogeneous nonequilibrium quantum fluids

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