  The transport of sound and heat, in the form of phonons, can be limited by
disorder-induced scattering. In electronic and optical settings the
introduction of chiral transport, in which carrier propagation exhibits parity
asymmetry, can remove elastic backscattering and provides robustness against
disorder. However, suppression of disorder-induced scattering has never been
demonstrated in non-topological phononic systems. Here we experimentally
demonstrate a path for achieving robust phonon transport in the presence of
material disorder, by explicitly inducing chirality through parity-selective
optomechanical coupling. We show that asymmetric optical pumping of a symmetric
resonator enables a dramatic chiral cooling of clockwise and counterclockwise
phonons, while simultaneously suppressing the hidden action of disorder.
Surprisingly, this passive mechanism is also accompanied by a chiral reduction
in heat load leading to optical cooling of the mechanics without added damping,
an effect that has no optical analogue. This technique can potentially improve
upon the fundamental thermal limits of resonant mechanical sensors, which
cannot be attained through sideband cooling.
