  The coherence and phase evolution of electrons in a mesoscopic system in the
Kondo correlated regime were studied. The Kondo effect, in turn, is one of the
most fundamental many-body effects where a localized spin interacts with
conduction electrons in a conductor. Results were obtained by embedding a
quantum dot (QD) in a double path electronic interferometer and measuring
interference of electron waves. The Phase was found to evolve in a range twice
as large as the theoretically predicted one. Moreover, the phase proved to be
highly sensitive to the onset of Kondo correlation, thus serving as a new
fingerprint of the Kondo effect.
