Evidence for Many-Electron Composite Charge Excitations in a Coulomb Glass

Coulomb interactions in a Coulomb glass system may make the current carrying excitations more complex entities than single point particles. We investigate this question in non-metallic Si:B by examining interaction energy scales in DC transport, low-frequency noise, and single-particle tunneling. The charge carriers responsible for direct current transport have a significantly lower Coulomb energy scale than single-particle point charges introduced by tunneling. The data suggest that current is carried by composite excitations composed of the correlated motions of many electrons.