title: Tight-binding approach to overdamped Brownian motion on a bichromatic periodic potential.
abstract: We present a theoretical treatment of overdamped Brownian motion on a time-independent bichromatic periodic potential with spatially fast- and slow-changing components. In our approach, we generalize the Wannier basis commonly used in the analysis of periodic systems to define a basis of S states that are localized at local minima of the potential. We demonstrate that the S states are orthonormal and complete on the length scale of the periodicity of the fast-changing potential, and we use the S-state basis to transform the continuous Smoluchowski equation for the system to a discrete master equation describing hopping between local minima. We identify the parameter regime where the master equation description is valid and show that the interwell hopping rates are well approximated by Kramers' escape rate in the limit of deep potential minima. Finally, we use the master equation to explore the system dynamics and determine the drift and diffusion for the system.
authors.affiliation: Scion, Private Bag 3020, Rotorua 3046, New Zealand and Department of Physics, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand.
authors.forename: P T T
authors.initials: PT
authors.lastname: Nguyen
authors.affiliation: Scion, Private Bag 3020, Rotorua 3046, New Zealand.
authors.forename: K J
authors.initials: KJ
authors.lastname: Challis
authors.affiliation: Department of Physics, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand.
authors.forename: M W
authors.initials: MW
authors.lastname: Jack
mesh_terms: D004058:Diffusion; D008962:Models, Theoretical; D009038:Motion