Abstract
Coupling a system to a nonthermal environment can profoundly affect the phase diagram of the closed system, giving rise to a special class of dissipation-induced phase transitions. Such transitions take the system out of its ground state and stabilize a higher-energy stationary state, rendering it the sole attractor of the dissipative dynamics. In this work, we present a unifying methodology, which we use to characterize this ubiquitous phenomenology and its implications for the open system dynamics. Specifically, we analyze the closed system's phase diagram, including symmetry-broken phases, and explore their corresponding excitations' spectra. Opening the system, the environment can overwhelm the system's symmetry-breaking tendencies, and changes its order parameter. As a result, isolated distinct phases of similar order become connected, and new phase-costability regions appear. Interestingly, the excitations differ in the newly-connected regions through a change in their symplectic norm, which is robust to the introduction of dissipation. As a result, by tuning the system from one phase to the other across the dissipation-stabilized region, the open system fluctuations exhibit an exceptional point-like scenario, where the fluctuations become overdamped, only to reappear with an opposite sign in the dynamical response function of the system. The overdamped region is also associated with squeezing of the fluctuations. We demonstrate the pervasive nature of such dissipation-induced phenomena in two prominent examples, namely in parametric resonators and in light-matter systems. Our work draws a crucial distinction between quantum phase transitions and their zero-temperature open system counterparts.
Highlights
In equilibrium and at zero temperature, we observe socalled quantum phase transitions (PTs), which are generally described through changes in the system’s Ginzburg-Landau (GL) energy functional and its symmetries as a control parameter is tuned [1], see Fig. 1(a)
When studying a system comprised of many degrees of freedom, e.g., an ensemble of harmonic oscillators, we study the mean-field (Landau-Ginzburg) energy functional, defined for ai → αi, where αi is a complex number corresponding to the semiclassical limit of the operator ai, and i iterates over all N degrees of freedom of the system
As in the Kerr parametric oscillator (KPO), this feature survives the introduction of dissipation and, we show that the e-normal phase (NP) becomes a dissipation-stabilized steady state
Summary
In equilibrium and at zero temperature, we observe socalled quantum phase transitions (PTs), which are generally described through changes in the system’s Ginzburg-Landau (GL) energy functional and its symmetries as a control parameter is tuned [1], see Fig. 1(a). The controllability, offered by numerous contemporary experimental platforms, such as cold atoms [3,4], trapped ions [5,6], superconducting circuits [7,8], and exciton-polariton cavities [9,10], placed out-of-equilibrium PTs at the avantgarde of contemporary research This has entailed the development of methods and concepts to characterize outof-equilibrium PTs, ranging from mean-field semiclassical equations of motion (EOM) and their corresponding fluctuations [2], to Keldysh action formalism [11,12] and third quantization [13,14], alongside with the study of exceptional points [15,16] and Liouvillian gaps [17,18].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
