Quantum ballistic transport in in-plane-gate transistors showing onset of a novel ferromagnetic phase transition

Abstract

We study one-dimensional transport in focused-ion-beam written in-plane-gate transistors on III-V heterostructures at moderately low temperatures at zero bias without any external magnetic field applied. In accordance with a recent proposal of A. Gold and L. Calmels, Valley- and spin-occupancy instability in the quasi-one-dimensional electron gas, Phil. Mag. Lett. 74, 33-42 (1996) and earlier experimental data, we observe plateaux in the source-drain conductivity considered as a function of the gate voltage, not only at multliples of 2e^2/h but also clearly at e^2/h, just before the channel closes to zero conductivity. This may be interpreted as a many electron effect, namely as a novel ballistic ferromagnetic ground state evading standard descriptions and theorems.