Overdamped Langevin dynamics in a periodic sawtooth potential U(x) of period L=1 (rising over fraction a, falling over 1-a) that is switched on and off:
dx = -(U'(x)/gamma) s(t) dt + sqrt(2 kT dt / gamma) xi
s(t) = 1 (on) or 0 (off), switched at the flash rate
drift J = d/dt
While off, particles diffuse symmetrically; when it turns on they slide into the nearest minimum. Because the sawtooth is asymmetric, more particles land in the next well forward than backward, giving net transport out of equilibrium. With the potential always on (equilibrium) or a symmetric tooth (a=0.5) the drift vanishes - consistent with the second law.