ANOMALOUS MAGNETORESISTANCE NEAR SUPERCONDUCTING TRANSITION-TEMPERATURE IN A MESOSCOPIC ALUMINUM WIRE

We have observed an anomalous magnetoresistance (MR) in a mesoscopic aluminum wire near the superconducting transition temperature. The anomaly exists in a region of low magnetic field less than 12.5 G and within the narrow temperature region where the Ginzburg-Landau coherence length exceeds half the distance between the voltage probes. It consists of a ''mesa'' or ''peak''-type MR centered around zero field (negative MR) with zero resistance outside the field region; in other words, the sample undergoes a normal-superconducting-normal transition as the magnetic field increases. Satellite peaks around the mesa MR were also observed for a very narrow range of temperature. We speculate that the sample size and dimensionality play an important role in these phenomena, but the origin is unclear.