Subband spacings of quasi-one-dimensional inversion channels on InSb

In metal-oxide-semiconductor structures on InSb we measure the static and the far-infrared conductivity of an array of narrow inversion channels that exhibit quantization into one-dimensional (1D) subbands. From oscillations in the static magnetoresistivity we determine the single-particle 1D subband spacings. These energies are compared with intersubband energies of transitions between the 1D subbands obtained by far-infrared Fourier spectroscopy. We find that depolarization and exciton shifts account for about 20% of the intersubband energies at an electron density nₗ=3×{}10⁶ cm^-1.