Temperature-induced spin-coherence dissipation in quantum dots

The temperature dependence of electron-spin coherence in singly negatively charged (In,Ga)As/GaAs quantum dots is studied by time-resolved Faraday rotation. The decoherence time T-2 is constant on the microsecond scale for temperatures below 15 K; for higher temperatures it shows a surprisingly sharp drop into the nanosecond range. The decrease cannot be explained through inelastic scattering with phonons, and it may be related to elastic scattering due to phonon-mediated fluctuations of the hyperfine interaction.