Vol. 41 (2010) ACTA PHYSICA POLONICA B No 5 RESONANT DIFFUSION IN PULSATED DEVICES ∗ Marcello Borromeo a,b , Fabio Marchesoni b,c a Dipartimento di Fisica, Università di Perugia, 06123 Perugia, Italy b Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, 06123 Perugia, Italy c Dipartimento di Fisica, Università di Camerino, 62032 Camerino, Italy (Received January 25, 2010) Diffusion of an overdamped Brownian particle on a symmetric peri- odic substrate is investigated in the presence of pulsated perturbations of two kinds: (i) stepwise lateral displacements (flashing substrate), and (ii) instantaneous tilts (shot noise). Pulses are applied in either periodic or random sequences with assigned mean (bias) and average waiting time (time constant). At zero bias, the diffusion coefficient of the particle can be greatly enhanced by tuning the time constant. Such a diffusion resonance should not be mistaken for the excess diffusion peaks earlier reported for finite biases. PACS numbers: 05.60.–k, 66.10.C–, 82.75.–z 1. Introduction Brownian diffusion on a periodic substrate is often affected by (i) model A: instantaneous lateral shifts of the substrate (flashing substrate) and (ii) model B: external kicks corresponding to instantaneous substrate tilts (shot noise). Both jittering mechanisms have been advocated to model trans- port at the micro- and nanoscales [1,2]. Historically, models of type B were introduced first, originally, to interpret the output of classical electronic de- vices [3], and more recently, to engineer quantum devices subject to shot noise of either electronic [4] or photonic nature [5]. Prominent applications of model A include molecular motors at the cellular level [2,6], where flashing is caused by power strokes from the chemical energy source (like the hydrol- ysis of a single ATP molecule), tunable optical lattices for cold atoms [7], where substrate shifts are associated to degenerate atomic levels, and elec- tromechanical sieves, e.g., for the electrophoresis of DNA strands [8]. * Presented at the XXII Marian Smoluchowski Symposium on Statistical Physics, Zakopane, Poland, September 12–17, 2009. (1093)