H Drexler, W Hansen, S. Manus
We report capacitance and far-infrared absorption measurements on quantum wires in which only the lowest one-dimensional subband is occupied. The wires are generated in special MISFET-type AlAs/GaAs heterojunctions with an interdigitated gate. Very pronounced steps in the capacitance as function of gate voltage reflect the onset of one-dimensional subbands. Additionally, in the one-dimensional quantum limit at very low electron density we observe a substructure which we interpret as a consequence of the renormalization of the effective confinement by electron-electron-interaction. Resonantly absorbed far-infrared radiation leads to a change of the sample capacitance and therefore allows us to investigate the collective excitations in the electron wires. We find that in our devices the fundamental one-dimensional intersubband resonance is tunable over a wide range up to 10.5 meV.