Effective interactions for self-energy. II. Application to electron and electron-hole liquids

Effective masses in an electron gas and an electron-hole liquid are calculated for different values of $r_s$ and of the ratio $M_h$/$M_e$ (in the case of the electron-hole liquid) using the self-energy expressions derived in the preceding paper [Ng and Singwi, Phys. Rev. B 34, 7738 (1986)]. In the case of an electron gas, it is found that spin-fluctuation effects lead to an appreciable amount of mass enhancement for metallic $r_s$ values, whereas in the case of an electron-hole liquid, both spin and density fluctuations are important in determining the quasiparticle properties.