Ensemble-average spectrum of Aharonov-Bohm conductance oscillations: Evidence for spin-orbit-induced Berry's phase

We have experimentally investigated Aharonov-Bohm conductance oscillations in two-dimensional tings in the presence of a strong Rashba spin-orbit interaction. The peak of the ensemble average spectrum corresponding to the h/e oscillations is split in several samples. We argue that the splitting originates from the geometric phase acquired by an electron spin under the influence of the spinorbit interaction. Our results demonstrate how the ensemble average spectrum provides information otherwise not easily accessible.