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Some remarks on 'superradiant' phase transitions in light-matter systems
Stockholm University, Faculty of Science, Department of Physics.
Number of Authors: 2
2017 (English)In: Journal of Physics A: Mathematical and Theoretical, ISSN 1751-8113, E-ISSN 1751-8121, Vol. 50, no 17, 174002Article in journal (Refereed) Published
Abstract [en]

In this paper we analyze properties of the phase transition that appears in a set of quantum optical models; Dicke, Tavis-Cummings, quantum Rabi, and finally the Jaynes-Cummings model. As the light-matter coupling is increased into the deep strong coupling regime, the ground state turns from vacuum to become a superradiant state characterized by both atomic and photonic excitations. It is pointed out that all four transitions are of the mean-field type, that quantum fluctuations are negligible, and hence these fluctuations cannot be responsible for the corresponding vacuum instability. In this respect, these are not quantum phase transitions. In the case of the Tavis-Cummings and Jaynes-Cummings models, the continuous symmetry of these models implies that quantum fluctuations are not only negligible, but strictly zero. However, all models possess a non-analyticity in the ground state in agreement with a continuous quantum phase transition. As such, it is a matter of taste whether the transitions should be termed quantum or not. In addition, we also consider the modifications of the transitions when photon losses are present. For the Dicke and Rabi models these non-equilibrium steady states remain critical, while the criticality for the open Tavis-Cummings and Jaynes-Cummings models is completely lost, i. e. in realistic settings one cannot expect a true critical behaviour for the two last models.

Place, publisher, year, edition, pages
2017. Vol. 50, no 17, 174002
Keyword [en]
Dicke, quantum Rabi, Jaynes-Cummings, quantum phase transition, open quantum system
National Category
Physical Sciences Mathematics
Identifiers
URN: urn:nbn:se:su:diva-142374DOI: 10.1088/1751-8121/aa65dcISI: 000398155500001OAI: oai:DiVA.org:su-142374DiVA: diva2:1093020
Available from: 2017-05-04 Created: 2017-05-04 Last updated: 2017-05-04Bibliographically approved

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CiteExportLink to record
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  • apa
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