Dephasing in Open Quantum Dots

Shape-averaged magnetoconductance (weak localization) is used for the first time to obtain the electron phase coherence time ${\tau }_{\phi }$ in open ballistic GaAs quantum dots. Values for ${\tau }_{\phi }$ in the range of temperature T from 0.34 to 4 K are found to be independent of dot area, and are not consistent with the ${\tau }_{\phi }\propto T^{-2\mathrm{}}$ behavior expected for isolated dots. Surprisingly, ${\tau }_{\phi }\left(T\right)$ agrees quantitatively with the predicted dephasing time for disordered two-dimensional electron systems.