1/f Noise in a Coulomb Glass and in a Noninteracting Electron Glass

We show that 1=f noise is produced in a 3D electron glass by charge uctuations due to electrons hopping between isolated sites and a percolating network at low temperatures. The low frequency noise spectrum goes as ! with slightly larger than 1. This result together with the temperature dependence of and the noise amplitude are in good agreement with the recent experiments. These results hold true both for a noninteracting electron glass with a at density of states and for a Coulomb glass. In the latter case, the density of states has a Coulomb gap that lls in with increasing temperature. For a large Coulomb gap width, this density of states gives a dc conductivity with a hopping exponent of 0:75 which has been observed in recent experiments. For a small Coulomb gap width, the hopping exponent 0:5. At low temperatures the noise amplitude of a noninteracting electron glass increases linearly with temperature while the noise amplitude of a Coulomb glass increases quadratically.