COHERENCE AND PHASE-SENSITIVE MEASUREMENTS IN A QUANTUM-DOT

Via a novel interference experiment, which measures magnitude and phase of the transmission coefficient through a quantum dot in the Coulomb regime, we prove directly, for the first time, that transport through the dot has a coherent component. We find the same phase of the transmission coefficient at successive Coulomb peaks, each representing a different number of electrons in the dot; however, as we scan through a single Coulomb peak we find an abrupt phase change of . The observed behavior of the phase cannot be understood in the single particle framework. © 1995 The American Physical Society.