Pumping single-file colloids: Absence of current reversal

TL;DR

This paper analyzes the directed flow of colloidal particles in a traveling wave potential, revealing peaks in current without reversal phenomena, supported by analytic and simulation results.

Contribution

It provides an analytic perturbative solution for colloid transport in a traveling wave potential and highlights the absence of current reversal, contrasting with lattice models.

Findings

Peaks in directed current as a function of frequency, wavelength, and density.

Good agreement between analytic predictions and numerical simulations.

No current reversal observed with changing particle density.

Abstract

We consider the single-file motion of colloidal particles interacting via short-ranged repulsion and placed in a traveling wave potential, that varies periodically in time and space. Under suitable driving conditions, a directed time-averaged flow of colloids is generated. We obtain analytic results for the model using a perturbative approach to solve the Fokker-Planck equations. The predictions show good agreement with numerical simulations. We find peaks in the time-averaged directed current as a function of driving frequency, wavelength and particle density and discuss possible experimental realizations. Surprisingly, unlike a closely related exclusion dynamics on a lattice, the directed current in the present model does not show current reversal with density. A linear response formula relating current response to equilibrium correlations is also proposed.