Anomalous Magnetoresistance of the Electron Gas in a Restricted Geometry

The two-probe conductance of narrow (≃100 nm) silicon inversion layers at magnetic fields above $B\simeq 4$ T is found to be anomalous in several ways. The magnetoresistance is negative and very large; the conductance at high $B$ rises with carrier density in a series of steps; each step disappears at a separate temperature. The results suggest that new many-body effects result from quasi one-dimensional confinement.