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Excited-state quantum phase transitions in Dicke superradiance models
1Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstraße 36, D-10623 Berlin, Germany.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|October 16, 2013
Summary
We analyzed quantum phase transitions in Dicke superradiance models. Criticality is energy-dependent, showing similarities to the Lipkin-Meshkov-Glick model.
Area of Science:
- Quantum optics
- Condensed matter physics
- Statistical mechanics
Background:
- Dicke superradiance models exhibit complex quantum phenomena.
- Understanding excited-state quantum phase transitions (ESQPTs) is crucial for quantum systems.
- The semiclassical limit offers insights into macroscopic quantum behaviors.
Purpose of the Study:
- To derive analytical results for ESQPTs in Dicke superradiance models.
- To investigate the semiclassical behavior of these models.
- To identify critical phenomena and their dependencies.
Main Methods:
- Calculation of a partition sum restricted to Dicke states.
- Analysis of the derivative of the density of states.
- Examination of observables like atomic inversion and photon number fluctuations.
Main Results:
- Singular behavior in the density of states derivative was identified.
- Mean atomic inversion and boson number were calculated at arbitrary energies.
- Criticality was found to depend on energy and a parameter controlling rotating/counterrotating terms.
Conclusions:
- The study reveals energy-dependent criticality in Dicke models.
- An analogy was drawn to nonanalyticities observed in the Lipkin-Meshkov-Glick model.
- These findings contribute to understanding quantum phase transitions in open quantum systems.
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