THERMAL-STRESS-INDUCED AVERAGING OF THE AHARONOV-BOHM OSCILLATIONS IN SUBMICROMETER AU LOOPS

We have prepared submicrometer-size loops of very high purity Au. At low fields, magnetoconductance oscillations with flux period h/e and h/2e can be clearly observed. The sample-specific Aharonov-Bohm oscillations with flux period h/e are strongly modified by heating the Au loops up to T = 20 K. These modifications probably result from the movement of dislocation line segments due to the thermal stress. The "annealing" at T = 20 K allows us to simulate the stochastic impurity averaging of the h/e oscillations and to reconstruct the low-field h/2e oscillations caused by the coherent backscattering around the loop. This h/2e signal is described very well by the weak electron localization theory, which takes into account the detailed geometry of the voltage and current probes.