Are super-radiant phase transitions possible?

J. M. Knight*, Y. Aharonov, G. T.C. Hsieh

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

61 Scopus citations


An argument is given which rules out super-radiant phase transitions in which the atomic states involved are connected by electric-dipole matrix elements. The argument is based on gauge invariance, and is valid even in the presence of direct interatomic interactions. Its relevance is demonstrated by presenting a number of two-level models exhibiting super-radiant phase transitions which are not forbidden by previous sum-rule arguments. As a preliminary to the argument, the nature of the super-radiant phase transition is discussed, and a simple model is given which reproduces its main features. It is argued, finally, that in at least one case in which our argument fails a super-radiant phase transition is possible in principle.

Original languageEnglish
Pages (from-to)1454-1462
Number of pages9
JournalPhysical Review A
Issue number4
StatePublished - 1978


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