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The Frequency Dependent Conductivity of Electron Glasses

E. Helgren·N. P. Armitage·G. Gruner
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Abstract

Results of DC and frequency dependent conductivity in the quantum limit, i.e. hw > kT, for a broad range of dopant concentrations in nominally uncompensated, crystalline phosphorous doped silicon and amorphous niobium-silicon alloys are reported. These materials fall under the general category of disordered insulating systems, which are referred to as electron glasses. Using microwave resonant cavities and quasi-optical millimeter wave spectroscopy we are able to study the frequency dependent response on the insulating side of the metal-insulator transition. We identify a quantum critical regime, a Fermi glass regime and a Coulomb glass regime. Our phenomenological results lead to a phase diagram description, or taxonomy, of the electrodynamic response of electron glass systems.

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E. Helgren, N. P. Armitage, G. Gruner. 2003-03-27. The Frequency Dependent Conductivity of Electron Glasses. https://doi.org/10.1103/physrevb.69.014201

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