Spin dynamics in electrochemically charged CdSe quantum dots

We use time-resolved Faraday rotation to measure coherent spin dynamics in colloidal CdSe quantum dots charged in an electrochemical cell at room temperature. Filling of the 1Sₑ electron level is demonstrated by the bleaching of the 1Sₑ-1S3∕2 absorption peak. One of the two Land\'e g factors observed in uncharged quantum dots disappears upon filling of the 1Sₑ electron state. The transverse spin-coherence time, which is over 10.3em0exns and is limited by inhomogeneous dephasing, also appears to increase with charging voltage. The amplitude of the spin precession signal peaks near the half-filling potential. Its evolution at charging potentials without any observable bleaching of the 1Sₑ-1S3∕2 transition suggests that the spin dynamics are influenced by low-energy surface states.