COUPLING OF LATERAL AND VERTICAL ELECTRON MOTION IN GAAS-ALXGA1-XAS QUANTUM WIRES AND DOTS

Electronic excitations in AlxGa1-xAs-GaAs quantum wires and quantum do ts have been investigated by means of resonant inelastic light scatter ing. At low frequencies, we find quasi-one-dimensional and quasi-zero- dimensional confined plasmons. Interestingly, we observe, at higher fr equencies, not only the original two-dimensional (2D) intersubband exc itations, but additional modes omega(k) in polarized scattering geomet ry. The experimental finding is that the frequencies of these modes ob ey the relation omega(k)(2) approximate to omega(2D)(2)+omega(1D/0D)(2 ), where omega(2D) is the frequency of the vertical intersubband charg e-density excitation. omega(1D) is a lateral quasi-one-dimensional con fined plasmon frequency in wires and omega(0D) is the frequency of a q uasi-zero-dimensional confined plasmon in dots. This relation shows th at the additional modes are collective charge-density excitations, whi ch occur due to a coupling of lateral and vertical electron motion.