DIFFRACTION, PHASE BREAKING, AND HALL ANOMALIES IN QUANTUM DOTS

We present a theory of the Hall effect in a quantum dot coupled to Hall and current leads by narrow constrictions. A magnetic-diffraction effect is described which results in a series of deep minima in the Hall resistance persisting to temperatures T > 1 K, robustness that is unique among mesoscopic quantum interference phenomena. At higher T, phase breaking causes an anomalous "last" Hall plateau at R(H) = h/4e2 and, at higher B, a plateau near the single-mode quantum Hall value R(H) = h/2e2. We explain the surprising behavior of the Hall resonances observed by Ford et al. (preceding paper) in quantum-wire junctions.