Environmental coupling and phase breaking in open quantum dots

Studies of electron phase coherence in open quantum dots reveal a subtle interplay between geometry and materials-related considerations. Suppressing environmental coupling, by reducing the width of the quantum point contact leads, a strong suppression of dephasing is observed. The magnitude of the phase-breaking time in this high-resistance regime shows large variations from device to device, indicative of a sensitivity to the specific disorder configuration in the dot. In order to account for our observations, we suggest an interpretation of phase breaking which invokes the discrete nature of the level spectrum in the open dots and which emphasizes the role of the quantum point contacts in selectively exciting cavity eigenstates.