COLLECTIVE SPIN-DENSITY EXCITATIONS IN A III-V SEMICONDUCTOR QUANTUM-WELL

We study the spin-density excitations in a III-V semiconductor quantum well, where the single-particle energies are spin split due to the sp in-orbit coupling. The vertex corrections to the polarizability are tr eated within a Fermi-liquid scheme. It is found that the vertex correc tions cause the appearance of one longitudinal and two transverse coll ective spin-density excitation modes with frequencies red shifted with respect to the single-particle spin splitting. The calculated Raman s pectrum shows strong angular and polarization dependence of the collec tive and single-particle Raman peaks due to interference of the spinor amplitudes.