Quantum beating in ring conductance: Observation of spin chiral states and Berry's phase

We propose and demonstrate experimentally a novel configuration for observing spin interference effects in mesoscopic rings. Using this configuration, in which the conducting ring and the tangential current lead form a single collimating contact, we have observed the spin quantum beating in the Aharonov-Bohm conductance oscillations. We demonstrate that the, beating is the result of the superposition of two independent interference signals associated with two orthogonal states arising from intrinsic spin-orbit interactions. Our work demonstrates the signature of the spin Berry phase in the conductance of quantum rings.