Abrupt change of the electronic properties of semiconductor single quantum well systems near the one-subband - two-subband occupied transition

P. G. BOLCATTO; C. R. PROETTO; P. GIUDICI; A. R. GOÑI

Beriloche

Congreso; On the physics at the Nanoscale; 2003

Photoluminescence experiments on semiconductor single quantum wells, SQW(Figure 1) reveal an abrupt change in its electronic structure when the Fermilevel touches the bottom of the lower unoccupied subband (Figure 2).By the other hand, Inelastic Light Scattering measurements, which giveinformation of the collective excitations of the system, also shown an abruptchange in the electronic properties (Figure 3).In this work, we calculate the charge-density (CDE) and spin-densityexcitations (SDE) of the SQW system by using the so-called Time DependentLocal Density Approximation. An analytical analysis of the excitation energies,allow us to discriminate the magnitude of the depolarization shift and thevertex corrections arising from the Hartree and exchange-correlation effects, both forCDE and SDE (Theory section).Our results, both experimental and theoretical, indicate that the screenedcoulomb interaction is the major responsible of the remarkable change in theexcitations when the total electronic density is modified (Figure 4).