Quantum Beating in Ring Conductance: Observation of Spin Chiral States and Berry's phase

Using singly connected rings with a collimating contact to current leads, we have observed the spin quantum beating in the Aharonov-Bohm conductance oscillations. We demonstrate that the beating is a result of the superposition of two independent interference patterns associated with two orthogonal spin chiral states arising from intrinsic spin-orbit interactions. Our work provides the conclusive evidence of the spin Berry's phase in the conductance of quantum rings.