Depinning transition of self-propelled particles

Depinning transitions occur when a threshold force must be applied to drive an otherwise immobile system. For the depinning of colloidal particles from a corrugated landscape, we show how active noise due to self-propulsion impacts the nature of this transition, depending on the speed and the dimensionality $d$ of rotational Brownian motion: the drift velocity exhibits the critical exponent 1/2 for quickly reorienting particles, which changes to $d\mathrm{/}2$ for slow ones; in between these limits, the drift varies superexponentially. Different giant diffusion phenomena emerge in the two regimes. Our predictions extend to systems with a saddle-node bifurcation in the presence of a bounded noise. Moreover, our findings suggest that nonlinear responses are a sensitive probe of nonequilibrium behavior in active matter.