Anomalously narrow Coulomb gap
Zabrodskii A. G. , Andreev A. G.
Many-electron correlations are likely in the hopping motion of localized charge carriers when the impurity band is approximately half-filled. These correlations should make the Coulomb gap narrower than in the Efros-Shklovsku one-electron limit. A narrowing of this sort, by about an order of magnitude, has been observed experimentally in a "K=0.3" lot of samples of neutron-transmutation-doped Ge:Ga.