Dwell-time related saturation of phase coherence in ballistic quantum dots

We present our experimental investigations on the low-temperature (T) saturation of the electron phase coherence time TO in open ballistic quantum dots fabricated from InGaAs/InAlAs heterostructures. At high temperature, we observe that tau(phi) = aT(-p), with 2/3 < p < 2. The constant a is strongly influenced by the population of the second electronic subband in the quantum well. Below a temperature T-onset, in the range 0.5 K < T-onset < 5 K, tau(phi) saturates in all our samples. The condition for the occurrence of saturation is found to be T-phi, (sat) = tau(d), where T-phi,T- sat is the saturated coherence time and tau(d) is the dwell time. We discuss possible interpretations for this observation. (c) 2006 Elsevier B.V. All rights reserved.