  Directed transport of overdamped Brownian particles driven by fractional
Gaussian noises is investigated in asymmetrically periodic potentials. By using
Langevin dynamics simulations, we find that rectified currents occur in the
absence of any external driving forces. Unlike white Gaussian noises,
fractional Gaussian noises can break thermodynamical equilibrium and induce
directed transport. Remarkably, the average velocity for persistent fractional
noise is opposite to that for anti-persistent fractional noise. The velocity
increases monotonically with Hurst exponent for the persistent case, whereas
there exists an optimal value of Hurst exponent at which the velocity takes its
maximal value for the anti-persistent case.
