The electron dephasing time τϕ​ in a diffusive quantum dot is
calculated by considering the interaction between the electron and dynamical
defects, modelled as two-level system. Using the standard tunneling model of
glasses, we obtain a linear temperature dependence of 1/τϕ​,
consistent with the experimental observation. However, we find that, in order
to obtain dephasing times on the order of nanoseconds, the number of two-level
defects needs to be substantially larger than the typical concentration in
glasses. We also find a finite system-size dependence of τϕ​, which
can be used to probe the effectiveness of surface-aggregated defects.Comment: two-column 9 page