Conventional and unconventional Dicke models: Multistabilities and nonequilibrium dynamics

• URL: http://arxiv.org/abs/2307.05686v3
• Date: Wed, 31 Jan 2024 17:51:55 GMT
• Title: Conventional and unconventional Dicke models: Multistabilities and nonequilibrium dynamics
• Authors: Farokh Mivehvar
• Abstract summary: The stability and dynamics of the system in the thermodynamic limit are examined using a semiclassical approach. We perform small-scale full quantum-mechanical calculations, with results consistent with the semiclassical ones.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: The Dicke model describes the collective behavior of a sub-wavelength--size ensemble of two-level atoms (i.e., spin-1/2) interacting identically with a single quantized radiation field of a cavity. Across a critical coupling strength it exhibits a zero-temperature phase transition from the normal state to the superradiant phase where the field is populated and the collective spin acquires a nonzero $x$-component, which can be imagined as ferromagnetic ordering of the atomic spins along $x$. Here we introduce a variant of this model where two sub-wavelength--size ensembles of spins interact with a single quantized radiation field with different strengths. Subsequently, we restrict ourselves to a special case where the coupling strengths are opposite (which is unitarily equivalent to equal-coupling strengths). Due to the conservation of the total spin in each ensemble individually, the system supports two distinct superradiant states with $x$-ferromagnetic and $x$-ferrimagnetic spin ordering, coexisting with each other in a large parameter regime. The stability and dynamics of the system in the thermodynamic limit are examined using a semiclassical approach, which predicts non-stationary behaviors due to the multistabilities. At the end, we also perform small-scale full quantum-mechanical calculations, with results consistent with the semiclassical ones.

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