Mechanisms of Symmetry Breaking in a Multidimensional Flashing Particle Ratchet

What is it about?

Almost all ratchet theory papers use 1D models. However, experimental ratchets typically have a 3D transport layer, which, due to symmetry, can be treated as 2D. Usually the electric field is applied by electrodes under the transport layer, meaning the field is asymmetric in the z-direction (thickness) - it is a 2D potential, rather than 1D. In this work we classically simulated charged nanoparticles in water, transported by time-oscillating ratchet potentials. We found that the non-uniformity in the z-direction means the thickness of the transport layer is extremely important for effective transport. In agreement with the experimental studies on electron ratchets, we found that the decay in the z-direction allows us to use sine wave temporal drive, something which is not possible in 1D models. In this new symmetry-breaking mechanism in ratchets, spatial asymmetry is used in place of temporal asymmetry.

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