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Researchers investigated a quantum Rabi model with parametric amplification and both single- and two-photon decay processes, revealing novel dissipative phase transitions (DPTs). They discovered an "inverted" regime where superradiance occurs at weak coupling rather than strong coupling, contrary to typical behavior. The study identified four distinct composite phases and characterized the critical behavior of these transitions, including first- and second-order DPTs separated by a tricritical point, with their associated universality classes and scaling exponents.
Why it matters
This work advances our understanding of open quantum systems and light-matter interactions, which are fundamental to developing quantum technologies such as quantum sensors, quantum simulators, and photonic devices. The identification of novel phase transition mechanisms could inform the design of more efficient quantum optical systems and cavity quantum electrodynamics setups.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
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Abstract: We demonstrate a novel mechanism driving complex critical phenomena in open light-atom interacting systems by investigating a parametrically amplified quantum Rabi model (QRM) subject to both single- and two-photon decay. In the classical oscillator limit, four composite phases emerge, arising from the possible normal or superradiant regimes across the upper and lower spin branches. A mean-field analysis reveals that the two-photon decay activates the intrinsic nonlinearity of the QRM. The synergy of the coherent and dissipative two-photon processes, together with the spin-boson coupling, constitutes an “inverted” regime where superradiance emerges exclusively at weak coupling. This regime features first- and second-order superradiant DPTs separated by a tricritical point. Utilizing an adiabatic approach and the semi-classical Langevin formalism, we further study the steady-state structure beyond the mean-field level. The universality classes of the DPTs are identified, with the corresponding critical and finite-size scaling exponents derived and a scaling ansatz proposed to describe the critical behavior.
Source: Dissipative Phase Transitions in an Open Quantum Rabi Model with Two-Photon Processes