Many-body effects on the electronic and optical properties of bulk GaP

We present an ab-initio study of GaP bulk as a test case to show the importance of going beyond the single particle Density Functional Theory (DFT) scheme in the calculation of excited state properties. The inclusion of many-body effects within the GW approach for the determination of electronic gaps, and of excitonic effects in the calculations of the dielectric function, is discussed. Comparison with one-particle DFT results and with experimental data are presented.