Magnetoresistance calculations for a quantum wire with periodically modulated width

We present numerical calculations of the magnetoresistance in a ballistic quantum wire with periodically modulated width. Surprisingly, the negative magnetoresistance peak is found to persist to a field strength which is two orders of magnitude larger than in single quantum dots. In the weak B -field regime, our results are in good agreement with recent experiments. We argue that the wide peak is due to multiple backscattering among the segments of the wire, leading to a novel weak localization effect.