INDICATIONS OF EFFECTS OF PHONON-ROTON STATES ON ELECTRONIC TRANSPORT

In this paper we report strong indications of the effects of phonon-ro ton states on electronic transport. Under conditions where the wavevec tor Q(p) of these states is close to 2k(F), inelastic umklapp-scatteri ng effects of the conduction electrons with phonon-roton states can oc cur. Below a characteristic temperature T0, under which the electronic energy is too low to excite these states, the inelastic umklapp scatt ering disappears, leaving the elastic umklapp scattering on the static structure and the inelastic scattering on long-wavelength phonons (De bye phonons). The variation in the scattering behaviour with temperatu re causes pronounced transport anomalies. The thermopower, for example , exhibits a kink at T0 and large deviations from the free-electron be haviour above T0. This effect is responsible for the different sign of the thermopower to the Hall coefficient at elevated temperatures, a l ong-standing problem which often exists in liquid and amorphous metals . Whereas indications of the inelastic umklapp scattering are also vis ible in the resistivity, seen as an inflection point where the resisti vity which was increasing starts to decrease, the Hall effect seems to be unaffected.