Theory of Quasiparticle Energies in Alkali Metals

The quasiparticle and structures of Na and Li are calculated by evaluation of the electron self-energy to first order in the dynamically screened Coulumb interaction. For Na, our results explain quantitatively the large bandwidth reduction observed in recent angle-resolved photoemission experiments. The inclusion of exchange-correlation effects in the dielectric screening and the requirement that the energy dependence of the electron Green's function be treated self-consistently are found to be important in obtaining the correct bandwidths.