Type: Article
Publication Date: 2019-12-18
Citations: 109
DOI: https://doi.org/10.1103/physrevlett.123.254101
We study the transition between integrable and chaotic behavior in dissipative open quantum systems, exemplified by a boundary driven quantum spin chain. The repulsion between the complex eigenvalues of the corresponding Liouville operator in radial distance $s$ is used as a universal measure. The corresponding level spacing distribution is well fitted by that of a static two-dimensional Coulomb gas with harmonic potential at inverse temperature $\ensuremath{\beta}\ensuremath{\in}[0,2]$. Here, $\ensuremath{\beta}=0$ yields the two-dimensional Poisson distribution, matching the integrable limit of the system, and $\ensuremath{\beta}=2$ equals the distribution obtained from the complex Ginibre ensemble, describing the fully chaotic limit. Our findings generalize the results of Grobe, Haake, and Sommers, who derived a universal cubic level repulsion for small spacings $s$. We collect mathematical evidence for the universality of the full level spacing distribution in the fully chaotic limit at $\ensuremath{\beta}=2$. It holds for all three Ginibre ensembles of random matrices with independent real, complex, or quaternion matrix elements.