Quantum chaos in a deformable billiard: Applications to quantum dots

We perform a detailed numerical study of energy-level and wave-function statistics of a deformable quantum billiard focusing on properties relevant to semiconductor quantum dots. We consider the family of Robnik billiards generated by simple conformal maps of the unit disk; the shape of this family of billiards may be varied continuously at fixed area by tuning the parameters of the map. The classical dynamics of these billiards is well understood and this allows us to study the quantum properties of subfamilies, which span the transition from integrability to chaos, as well as families at approximately a constant degree of chaoticity (Kolmogorov entropy). In the regime of hard chaos we find that the statistical properties of interest are well described by random-matrix theory and are completely insensitive to the particular shape of the dot. However, in the nearly integrable regime nonuniversal behavior is found. Specifically, the level-width distribution is well described by the predicted ${\mathrm{\chi }}^2$ distribution both in the presence and absence of magnetic flux when the system is fully chaotic; however, it departs substantially from this behavior in the mixed regime. The chaotic behavior corroborates the previously predicted behavior of the peak-height distribution for deformed quantum dots. We also investigate the energy-level correlation functions, which are found to agree well with the behavior calculated for quasi-zero-dimensional disordered systems.