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We study a paradigmatic driven-dissipative model, dubbed interpolating Dicke-Tavis-Cummings (IDTC), where a collection of two-level systems interact with both quadratures of a quantum cavity mode. The closed system exhibits rich physics, including discrete and continuous symmetry-breaking phase transitions meeting at a multicritical point. We show that the closed system's phase diagram is profoundly altered by the presence of dissipation, eliminating the presence of broken continuous symmetry transitions, leading to novel regions of coexistence of phases and the appearance of two tricritical points. Using Keldysh formalism, we explore the dynamical response of this fascinating new phase diagram. Surprisingly, we find that an additional intriguing dynamical phase transition manifests in the frequency response of the system. At the transition, low-energy particle- and hole-like processes change roles due to a soft mode gap closing.

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Oded Zilberberg, ETH Zurich
Seminar Room of the Institute of Physics II
Contact: S. Diehl