Non-ergodicity and fluctuations in mesoscopic insulators: The replica cooperon and diffuson

We explore the mesoscopic conductance fluctuations in the insulating regime within the Nguyen, Spivak, and Shklovskii model. We nd that fluctuations o f the log-conductance are persistent above the decorrelation field B-c in t he insulating regime. Using the replica approach, we derive the field coupl ing and fluctuations in terms of "cooperon" and "diffuson" analogs and dete rmine new corrections to temperature dependencies for small DeltaB. We also analyze the ergodicity of fluctuations in the log-conductance and its scal ing properties, and discuss the asymptotic validity of the usual criterion involving the commutability of disorder and field fluctuation averages.