English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We consider spin-boson models composed by a single bosonic mode and anensemble of $N$ identical two-level atoms. The situation where the couplingbetween the bosonic mode and the atoms generates real and virtual processes isstudied, where the whole system is in thermal equilibrium with a reservoir attemperature $\beta^{-1}$. Phase transitions from ordinary fluorescence tosuperradiant phase in three different models is investigated. First a modelwhere the coupling between the bosonic mode and the $j-th$ atom is via thepseudo-spin operator $\sigma^{,z}_{(j)}$ is studied. Second, we investigate thegeneralized Dicke model, introducing different coupling constants between thesingle mode bosonic field and the environment, $g_{1}$ and $g_{2}$ for rotatingand counter-rotating terms, respectively. Finally it is considered a modifiedversion of the generalized Dicke model with intensity-dependent coupling in therotating terms. In the first model the zero mode contributes to render thecanonical entropy a negative quantity for low temperatures. The last two modelspresents phase transitions, even when only Hamiltonian terms which generatesvirtual processes are considered.

Virtual Processes and Superradiance in Spin-Boson Models