ANOMALOUSLY NARROW COULOMB GAP

Many-electron correlations are likely in the hopping motion of localiz ed charge carriers when the impurity band is approximately half-filled . These correlations should make the Coulomb gap narrower than in the Efros-Shklovskii one-electron limit. A narrowing of this sort, by abou t an order of magnitude, has been observed experimentally in a ''K=0.3 '' lot of samples of neutron-transmutation-doped Ge:Ga.