Microwave AC Conductivity Spectrum of a Coulomb Glass
30 July 2001
We report the first observation of the transistion between interacting and non-interacting AC conductivity sigma(omega) in a doped semiconductor in its Coulomb glass state near T = 0 K. The transition manifests itself as a crossover from approximately linear frequency dependence below ~10 Ghz, to quadratic dependence above ~15 GHz. The crossover frequency is closely related to the Coulomb interaction energy relevant to quasiparticle transport. However, the quantitative form of the transition is not well described by existing theory.