Spacing ratios in mixed-type systems

The distribution of the consecutive level-spacing ratio is now widely used as a tool to distinguish integrable from chaotic quantum spectra, mostly due to its avoidance of the numerical spectral unfolding. Like the use of the Rosenzweig-Porter approach to obtain the Berry-Robnik distribution of level spacings in mixed-type systems, in this paper, we extend this approach to analytically derive the distribution of spacing ratios for random matrices comprised of independent integrable blocks and chaotic blocks. We have numerically confirmed this analytical result using random matrix theory in paradigmatic models such as the quantum kicked rotor and the Hénon-Heiles system.