MANY-BODY VERTEX CORRECTIONS ON QUASI-PARTICLE PROPERTIES OF 2-DIMENSIONAL ELECTRON-SYSTEMS

We calculate theoretically the lifetime, the effective mass, the renormalization factor, and the exchange-correlation-induced band-gap renormalization for quasiparticles in two-dimensional electron systems. In our theory we go beyond the usual random-phase approximation by including many-body vertex corrections of the Hubbard type in the self-energy and the dielectric function of the electron gas. We find that in narrow quantum wells vertex corrections may be quantitatively significant, bringing calculated results close to the experimental data, especially for the case of the band-gap renormalization. In general, vertex correction is found to be more important for narrower quantum wells and for lower electron densities.