ANOMALOUS RXX IN THE QUANTUM HALL REGIME DUE TO IMPURITY-BOUND STATES

We present a direct numerical calculation of R(xx) and R(xy) in a rectangular Hall bar with a single impurity from the low-field to the quantum Hall regime. A resonance peak in R(xx) is observed in the quantum Hall regime, which disappears if the impurity is removed. The current-flow pattern at the peak clearly shows the coupling of edge states on opposite edges through the impurity, thus confirming the model proposed by Jain and Kivelson [Phys. Rev. Lett. 60, 1542 (1988)]. A clear signature of the impurity-bound state is also observed in the local density of states. Further confirmation is obtained by studying the effect of the size of the impurity on the location and height of the peak.