Acoustic plasmons in a two-band metal

The properties of acoustic plasmon excitations and the conditions for their existence in a metal with two overlapping bands one of which is narrow (d-band) and the other broad (s-band) are discussed. Model calculations in which the d-electrons are treated in the tight-binding approximation and the s-electrons are assumed to be free are presented. The prospects for finding well defined acoustic plasmons in a real system are examined. The example of the V₃Ga crystal is considered in some detail.