DEPHASING IN OPEN QUANTUM DOTS

Shape-averaged magnetoconductance (weak localization) is used to measu re the electron phase coherence time tau(phi) in open ballistic GaAs q uantum dots with temperature T ranging from 0.1 to 4 K. tau(phi)(T) is not consistent with the tau(phi) proportional to T-2 behavior expecte d for isolated dots, and does not saturate over the temperature range measured. Surprisingly, tau(phi)(T) agrees quantitatively with predict ed dephasing times for disordered two-dimensional electron systems, su ggesting the presence of a Nyquist phase relaxation mechanism. (C) 199 8 Elsevier Science B.V. All rights reserved.