title: Measurements of the complex conductivity of NbxSi(1-x) alloys on the insulating side of the metal-insulator transition.
abstract: We have conducted temperature and frequency dependent transport measurements in amorphous NbxSi1-x samples in the insulating regime. We find a temperature dependent dc conductivity consistent with variable range hopping in a Coulomb glass. The frequency dependent response in the millimeter-wave frequency range can be described by the expression sigma(omega) varies with (-iota omega)(alpha) with the exponent somewhat smaller than 1. Our ac results are not consistent with extant theories for the hopping transport.
authors.affiliation: Department of Physics and Astronomy, University of California, Los Angeles, 90095, USA.
authors.forename: E
authors.initials: E
authors.lastname: Helgren
authors.forename: G
authors.initials: G
authors.lastname: Grüner
authors.forename: M R
authors.initials: MR
authors.lastname: Ciofalo
authors.forename: D V
authors.initials: DV
authors.lastname: Baxter
authors.forename: J P
authors.initials: JP
authors.lastname: Carini