Dicke model: entanglement as a finite size effect

We analyze Dicke model at zero temperature by matrix diagonalization to determine the entanglement in the ground state. In the infinite system limit the mean field approximation predicts a quantum phase transition from a non-interacting state to a Bose-Einstein condensate at a threshold coupling. We...

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Bibliographic Details
Published inarXiv.org
Main Authors Tsyplyatyev, O, Loss, D
Format Paper Journal Article
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 15.07.2009
Subjects
Approximation
Coupling
Entanglement
Ground state
Mathematical analysis
Phase transitions
Physics - Mesoscale and Nanoscale Physics
Quantum theory
Size effects
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Summary:We analyze Dicke model at zero temperature by matrix diagonalization to determine the entanglement in the ground state. In the infinite system limit the mean field approximation predicts a quantum phase transition from a non-interacting state to a Bose-Einstein condensate at a threshold coupling. We show that in a finite system the spin part of the ground state is a bipartite entangled state, which can be tested by probing two parts of the spin system separately, but only in a narrow regime around the threshold coupling. Around the resonance, the size of this regime is inversely proportional to the number of spins and shrinks down to zero for infinite systems. This spin entanglement is a non-perturbative effect and is also missed by the mean-field approximation.
ISSN:2331-8422
DOI:10.48550/arxiv.0907.2553