Raman Spectroscopy of Quantum Wires and Dots: Magnetoplasmons and Edge-Spin-Density Modes

We review recent magneto-Raman experiments on electronic excitations in GaAs–AlGaAs quantum wires and dots. We observe simultaneously collective spin-density and charge-density excitations (SDEs and CDEs), and also single-particle-like excitations. In a magnetic field, the CDEs (magnetoplasmons) exhibit a complex anticrossing behavior, which, in quantum wires, strongly depends on the direction of lateral wave-vector transfer. In quantum dots, we observe a splitting of the lowest spin-density mode in a magnetic field, very similar to the splitting of the magnetoplasmons. The lower branch can be interpreted as an edge-spin-density mode, where the electrons move on skipping orbits around the edge of the dot. In a microscopic model, we can identify transitions between electronic shells, which contribute to the observed low-energy SDEs of the quasiatomic system