Nonparabolic confinement in quantum wire superlattices.

The high-frequency polarizability of quantum wires in a novel metal-insulator-semiconductor fieldeffect transistor heterojunction is studied in the far-infrared regime. Whereas on conventional narrow quantum wires only the fundamental mode of the dimensional resonance is observed, the quantum wires investigated here exhibit higher harmonics. Additionally, at high electron densities and intermediate magnetic fields we observe a completely unexpected splitting of the fundamental mode. The behavior is discussed in view of nonparabolic confinement as well as interwire interaction