Many-Body Effects in diluted twodimensional electron gases from optical spectroscopy

P. GIUDICI; A. R. GOÑI; C. THOMSEN

Dresden

Encuentro; Fr¨uhjahrstagung der deutschen physikalischen Gesellschaft; 2003

Deutschen Physikalischen Gesellschaft

Many-body effects on the elementary excitation of the 2D electron gas formed in a GaAs/AlGaAs SQW are investigated using Photoluminescence and inelastic light-scattering. The electron density in the well is varied by applying a gate voltage. The electron system undergoes a first order phase transition, as the second subband becomes populated. Its first order character is evidenced by the sudden population of the second subband as well as by an abrupt renormalizationof the intersubband energy. The critical temperature of the transition is estimated to be 35 K, and  beyond this point the density of the second subband changes continuously. In this work we also present results of inelastic light-scattering measurements in a temperature range between 2 and 40 K. As the transition takes place we observe an abrupt change in the Coulomb interaction terms, which are obtained from  the energies of the measured excitations of the charge and spin.