Berlin 2014 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 39: Ultracold atoms, ions and BEC IV (with A)

Q 39.5: Talk

Thursday, March 20, 2014, 11:30–11:45, BEBEL E34

Excited-state quantum phase transitions in Dicke superradiance models — •Tobias Brandes — TU Berlin

We derive analytical results [1] for various quantities related to the excited-state quantum phase transitions in a class of Dicke superradiance models in the semiclassical limit. Based on a calculation of a partition sum restricted to Dicke states, we discuss the singular behavior of the derivative of the density of states and find observables such as the mean (atomic) inversion and the boson (photon) number and its fluctuations at arbitrary energies. Criticality depends on energy and a parameter that quantifies the relative weight of rotating versus counterrotating terms, and we find a close analogy to the logarithmic and jump-type nonanalyticities known from the Lipkin-Meshkov-Glick model.

[1] T. Brandes, Phys. Rev. E 88, 032133 (2013).