  We experimentally revisite the flow down an inclined plane of dense granular
suspensions, with particles of sizes in the micron range, for which thermal
fluctuations cannot be ignored. Using confocal microscopy on a miniaturized
set-up, we observe that, in contrast with standard granular rheology, the flow
profiles strongly depend on the particles size. Also, suspensions composed of
small enough particles flow at infinitesimal inclinations. From the velocity
measurements, an effective rheology is extracted in terms of a friction
coefficient as a fonction of the dimensionless shear rate (the viscous number),
and of the particle pressure normalized by the thermal pressure. Inspired by a
previous work [1], a phenomenological model based on the sum of a thermal
contribution describing the glass transition and an athermal contribution
capturing the jamming transition is developed, which reproduces well the
experimental observations. The model predicts the existence of a glassy
friction angle lower than the granular athermal friction angle, a signature of
the glass transition in the framework of a pressure imposed rheology.
