  In this work, the ratchet dynamics of Brownian particles driven by an
external sinusoidal (harmonic) force is investigated. The gating ratchet effect
is observed when another harmonic is used to modulate the spatially symmetric
potential in which the particles move. For small amplitudes of the harmonics,
it is shown that the current (average velocity) of particles exhibits a
sinusoidal shape as a function of a precise combination of the phases of both
harmonics. By increasing the amplitudes of the harmonics beyond the small-limit
regime, departures from the sinusoidal behavior are observed and current
reversals can also be induced. These current reversals persist even for the
overdamped dynamics of the particles.
