New universal conductance fluctuation of mesoscopic systems in the crossover regime from metal to insulator

We report a theoretical investigation on conductance fluctuation of mesoscopic systems. Extensive numerical simulations on quasi-one dimensional, two dimensional, and quantum dot systems with different symmetries (COE, CUE, and CSE) indicate that the conductance fluctuation can reach a new universal value in the crossover regime for systems with CUE and CSE symmetries. The conductance fluctuation and higher order moments vs average conductance were found to be universal functions from diffusive to localized regimes that depend only on the dimensionality and symmetry. The numerical solution of DMPK equation agrees with our result in quasi-one dimension. Our numerical results in two dimensions suggest that this new universal conductance fluctuation is related to the metal-insulator transition.