QUANTUM WIRES WITH A WIDELY TUNABLE CONFINING POTENTIAL

We report capacitance and far-infrared absorption measurements on quan tum wires in which only the lowest one-dimensional subband is occupied . The wires are generated in special MISFET-type AlAs/GaAs heterojunct ions with an interdigitated gate. Very pronounced steps in the capacit ance as function of gate voltage reflect the onset of one-dimensional subbands. Additionally, in the one-dimensional quantum limit at very l ow electron density we observe a substructure which we interpret as a consequence of the renormalization of the effective confinement by ele ctron-electron-interaction. Resonantly absorbed far-infrared radiation leads to a change of the sample capacitance and therefore allows us t o investigate the collective excitations in the electron wires. We fin d that in our devices the fundamental one-dimensional intersubband res onance is tunable over a wide range up to 10.5 meV.