Scaling of level statistics and critical exponent of disordered two-dimensional symplectic systems

The statistics of the energy eigenvalues at the metal-insulator transition of a two-dimensional disordered system with spin-orbit interaction is investigated numerically. The critical exponent nu is obtained from the finite-size scaling of the number J(0) which is related to the probability Q(n)(s) of having n energy levels within an interval of width s. In contrast to previous estimates, we find nu = 2.32 +/- 0.14 close to the value of the two-dimensional quantum Hall system.