  Using electrical transport experiments and shot noise thermometry, we find
strong evidence that "supercollision" scattering processes by flexural modes
are the dominant electron-phonon energy transfer mechanism in high-quality,
suspended graphene around room temperature. The power law dependence of the
electron-phonon coupling changes from cubic to quintic with temperature. The
change of the temperature exponent by two is reflected in the quadratic
dependence on chemical potential, which is an inherent feature of two-phonon
quantum processes.
