Theory for the complex dynamic structure factor of an electron gas

The anomaly observed in the dynamical structure factor S(k, omega ), of various metallic systems is explained by considering processes in which a plasmon decays into an electron-hole pair plus a plasmon in addition to the usual RPA single-pair final state. The splitting in the spectrum is shown to result from the existence of two poles in S(kz) for Imz<0 and k<2k F . The observed structure in S(k, omega ) is reproduced almost exactly.