The influence of environmental coupling on phase breaking in open quantum dots

Studies of the phase breaking time in open quantum dots reveal a value of the order of a few tens of picoseconds at low resistances, which increases by as much as one order of magnitude as the quantum point contact leads are narrowed to support just a few modes. In addition, the value of the phase breaking time in the high resistance regime shows considerable device dependent variations, indicative of a sensitivity of phase coherence to device dependent disorder. In order to account for these 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 dot eigenstates.