Paper detail

Anderson transition in a three dimensional kicked rotor

We investigate Anderson localization in a three dimensional (3d) kicked rotor. By a finite size scaling analysis we have identified a mobility edge for a certain value of the kicking strength $k = k_c$. For $k > k_c$ dynamical localization does not occur, all eigenstates are delocalized and the spectral correlations are well described by Wigner-Dyson statistics. This can be understood by mapping the kicked rotor problem onto a 3d Anderson model (AM) where a band of metallic states exists for sufficiently weak disorder. Around the critical region $k \approx k_c$ we have carried out a detailed study of the level statistics and quantum diffusion. In agreement with the predictions of the one parameter scaling theory (OPT) and with previous numerical simulations of a 3d AM at the transition, the number variance is linear, level repulsion is still observed and quantum diffusion is anomalous with $<p^2 > \propto t^{2/3}$. We note that in the 3d kicked rotor the dynamics is not random but deterministic. In order to estimate the differences between these two situations we have studied a 3d kicked rotor in which the kinetic term of the associated evolution matrix is random. A detailed numerical comparison shows that the differences between the two cases are relatively small. However in the deterministic case only a small set of irrational periods was used. A qualitative analysis of a much larger set suggests that the deviations between the random and the deterministic kicked rotor can be important for certain choices of periods. Contrary to intuition correlations in the deterministic case can either suppress or enhance Anderson localization effects.