TRANSPORT-PROPERTIES OF V-4 AND MO-4 CLUSTER COMPOUNDS - AN ELECTRON GLASS

DC and AC conductivity, thermopower and non-ohmic conduction propertie s have been reported for GaV4S8 and GaMo4Se4Te4. The transport propert ies indicate the formation of electron glass state at low temperature. In a simplified model the band spread of localised states, DOS and lo calisation length are estimated. Coulomb gap effects in variable range hopping (VRH) and AC conductivity sigma(ac)(omega) are found in the m ore ordered Mo-4 compound. Both the compounds show negative resistance behaviour at high current densities that may indicate the melting of the electron glass.