Nonsinusoidal current and current reversals in a gating ratchet.

Abstract

©2015 American Physical Society. We acknowledge financial support through: Grants No. FIS2011-24540 (N.R.Q.) and FIS2011-22644 ENFASIS (L.D.); from Ministerio de Economía y Competitividad (Spain); Grants No. FQM207 (N.R.Q.), and No. P09-FQM-4643 (N.R.Q.), from Junta de Andaluc´ıa (Spain); and especially a grant from the Alexander von Humboldt Foundation (Germany) through Research Fellowship for Experienced Researchers SPA 1146358 STP (N.R.Q.). Part of the calculations of this work were performed in the high capacity cluster for physics, funded in part by Universidad Complutense de Madrid, Spain and in part with Feder FUNDS. This is a contribution to the Campus of International Excellence of Moncloa, CEI Moncloa.The ability to implement adiabatic processes in the mesoscale is of key importance in the study of artificial or biological micro- and nanoengines. Microadiabatic processes have been elusive to experimental implementation due to the difficulty in isolating Brownian particles from their fluctuating environment. Here we report on the experimental realization of a microscopic quasistatic adiabatic process employing a trapped Brownian particle. We circumvent the complete isolation of the Brownian particle by designing a protocol where both characteristic volume and temperature of the system are changed in such a way that the entropy of the system is conserved along the process. We compare the protocols that follow from either the overdamped or underdamped descriptions, demonstrating that the latter is mandatory in order to obtain a vanishing average heat flux to the particle. We provide analytical expressions for the distributions of the fluctuating heat and entropy and verify them experimentally. Our protocols could serve to implement the first microscopic engine that is able to attain the fundamental limit for the efficiency set by Carnot.Ministerio de Economía y Competitividad (Spain)Junta de Andalucía (Spain)Alexander von Humboldt Foundation (Germany)Universidad Complutense de Madrid, SpainDepto. de Estructura de la Materia, Física Térmica y ElectrónicaFac. de Ciencias FísicasTRUEpu