Genuine Quantum effects in Dicke-type Models at large atom numbers
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866908653930414080 |
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| author | Müller, Kai Strunz, Walter T. |
| author_facet | Müller, Kai Strunz, Walter T. |
| contents | We investigate the occurrence of genuine quantum effects and beyond mean-field physics in the balanced and unbalanced open Dicke model with a large, yet finite number of atoms $N$. Such driven and dissipative quantum many-body systems have recently been realized in experiments involving ultracold gases inside optical cavities and are known to obey mean-field predictions in the thermodynamic limit $N\to\infty$. Here we show quantum effects that survive for large but finite $N$, by employing a novel open-system dynamics method that allows us to obtain numerically exact quantum dynamical results for atom numbers up to a mesoscopic $N\approx 1000$. While we find that beyond-mean-field effects vanish quickly with increasing $N$ in the balanced Dicke model, we are able to identify parameter regimes in the unbalanced Dicke model that allow genuine quantum effects to persist even for mesoscopic $N$. They manifest themselves in a strong squeezing of the steady state and a modification of the steady-state phase diagram that cannot be seen in a mean-field description. This is due to the fact that the steady-state limit $t\rightarrow \infty$ and thermodynamic limit $N\rightarrow \infty$ do not commute. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2503_03396 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Genuine Quantum effects in Dicke-type Models at large atom numbers Müller, Kai Strunz, Walter T. Quantum Physics Quantum Gases We investigate the occurrence of genuine quantum effects and beyond mean-field physics in the balanced and unbalanced open Dicke model with a large, yet finite number of atoms $N$. Such driven and dissipative quantum many-body systems have recently been realized in experiments involving ultracold gases inside optical cavities and are known to obey mean-field predictions in the thermodynamic limit $N\to\infty$. Here we show quantum effects that survive for large but finite $N$, by employing a novel open-system dynamics method that allows us to obtain numerically exact quantum dynamical results for atom numbers up to a mesoscopic $N\approx 1000$. While we find that beyond-mean-field effects vanish quickly with increasing $N$ in the balanced Dicke model, we are able to identify parameter regimes in the unbalanced Dicke model that allow genuine quantum effects to persist even for mesoscopic $N$. They manifest themselves in a strong squeezing of the steady state and a modification of the steady-state phase diagram that cannot be seen in a mean-field description. This is due to the fact that the steady-state limit $t\rightarrow \infty$ and thermodynamic limit $N\rightarrow \infty$ do not commute. |
| title | Genuine Quantum effects in Dicke-type Models at large atom numbers |
| topic | Quantum Physics Quantum Gases |
| url | https://arxiv.org/abs/2503.03396 |