Negative resistance fluctuations at resistance minima in narrow quantum hall conductors

Negative resistances are a signature of four-terminal resistance measurements. We construct a simple model of a localized impurity state in a four-probe conductor. A recently proposed multiprobe resistance formula is combined with the multichannel Breit-Wigner formalism to describe tunneling between edge states via the localized state. Deviations from the quantized Hall resistance are discussed and the symmetry with regard to magnetic field reversal is investigated. The model permits negative longitudinal resistance fluctuations which have been observed in recent experiments. © 1988 The American Physical Society.