UNIVERSAL CONDUCTANCE FLUCTUATIONS IN A MAGNETIC-FIELD

Conductance fluctuations in disordered metals are calculated numerically in the presence of a magnetic field. The conductivity is evaluated using the Kubo-Greenwood formula for a model with substitutional disorder. As in our previous work, our Hamiltonian is reminiscent of the Kronig-Penney model in that delta-function-like atomic potentials are specified by a single parameter. We study systems whose size is always larger than the elastic mean free path and fields whose strength is such that the flux entering the sample is always greater than the flux quantum. We confirm the delocalization of wavefunctions due to the effect of the magnetic field and observe the factor-of-2 reduction of conductance fluctuations predicted by theory in 2-d geometry.