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Some remarks on 'superradiant' phase transitions in light-matter systems

Some remarks on 'superradiant' phase transitions in light-matter systems
Some remarks on 'superradiant' phase transitions in light-matter systems
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.
1751-8113
1-22
Larson, Jonas
1f16d2fd-ac49-4c1c-8726-da6085ef3988
Irish, Elinor
b78b8d7c-c747-4437-bb6f-189186713998
Larson, Jonas
1f16d2fd-ac49-4c1c-8726-da6085ef3988
Irish, Elinor
b78b8d7c-c747-4437-bb6f-189186713998

Larson, Jonas and Irish, Elinor (2017) Some remarks on 'superradiant' phase transitions in light-matter systems. Journal of Physics A: Mathematical and Theoretical, 50 (17), 1-22, [174002]. (doi:10.1088/1751-8121/aa65dc).

Record type: Article

Abstract

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.

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Accepted/In Press date: 10 March 2017
e-pub ahead of print date: 29 March 2017
Published date: 28 April 2017

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Local EPrints ID: 413731
URI: http://eprints.soton.ac.uk/id/eprint/413731
ISSN: 1751-8113
PURE UUID: c1d274b1-3099-438c-9317-7d696aabdb90

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Date deposited: 01 Sep 2017 16:31
Last modified: 26 Nov 2021 06:22

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Contributors

Author: Jonas Larson
Author: Elinor Irish

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