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

Abstract

We present our experimental investigations on the low-temperature ( T) saturation of the electron phase coherence time τ φ in open ballistic quantum dots fabricated from InGaAs/InAlAs heterostructures. At high temperature, we observe that τ φ = 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, τ φ saturates in all our samples. The condition for the occurrence of saturation is found to be τ φ , sat= τ d, where τ φ , sat is the saturated coherence time and τ d is the dwell time. We discuss possible interpretations for this observation.