THERMALLY INDUCED CHARACTERISTIC-MAGNETORESISTANCE-PATTERN CHANGES ON A MESOSCOPIC GOLD WIRE

Mesoscopic systems exhibit magnetoresistance fluctuations that are caused by interference of the conduction electrons moving along different paths as they scatter off impurities and have their phase altered by a magnetic field. We have produced gold wires of submicrometer widths and have studied their magnetoresistance below 1 K. Clear, characteristic magnetoresistance patterns (CMRP's) were obtained that were stable over a period of several weeks. We have observed no changes of resistance as a function of time. We have observed changes on the CMRP's after warming up to 1 K. We interpret those changes as indications of thermally assisted hops of impurities. An estimate of the size of the barriers between impurity sites is made based on the frequency of the CRMP changes and on the theory of universal conductance fluctuations.