Fig. 8: Schematics of how a granular system explores its potential energy landscape.

Due to the particle surface roughness, the PEL has not only a structure on the particle scale d (green line), but also a micro-corrugation with a characteristic size ξ. Starting in the left metabasin (MB) of the PEL, the double arrows indicate the back and forth motion of the system during a shear cycle. a The dynamics for small roughness (ξ ≪ d) shows two regimes depending on whether the system leaves the MB during a cycle (blue arrow) or not (red arrow). b The dynamics for large roughness evolve smoothly with Γ since ξ becomes comparable to d.