Dissipation due to two-level systems in nano-mechanical devices
  We analyze the dissipation of the frequency vibrations of nano-mechanical devices. We show that the coupling between flexural modes and two-level systems leads to sub-ohmic dissipation. The inverse quality factor of the low energy vibrations depends on temperature as $Q^{-1} (T) \approx Q_0 + C T^{1/3}$, providing a quantitative description of the experimental data. 
C. Seoanez, F. Guinea, A. H. Castro Neto