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Measurements of the Complex Conductivity of NbxSi1-x Alloys on the Insulating Side of the Metal-Insulator Transition

Erik Helgren, George Grüner, Martin Ciofalo, David V. Baxter, John P. Carini

cond-mat.str-elarXiv:cond-mat/0103202

Abstract

We have conducted temperature and frequency dependent transport measurements in amorphous Nbx Si1-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) (- omega)alpha with the exponent somewhat smaller than one. Our ac results are not consistent with extant theories for the hopping transport.

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