Hidden heat transfer in equilibrium states implies directed motion in nonequilibrium states

TL;DR

This paper reveals that hidden heat transfer in equilibrium states is linked to directed motion in nonequilibrium states, providing insights into heat transfer mechanisms in systems like Feynman's ratchet.

Contribution

It introduces the concept of hidden heat transfer in equilibrium and establishes its quantitative relation to directed motion in nonequilibrium steady states.

Findings

Steps are associated with nonvanishing heat transfer even in equilibrium.

A quantitative relation exists between hidden heat transfer and directed motion.

The principle of heat transfer enhancement explains this relation.

Abstract

We study a class of heat engines including Feynman's ratchet, which exhibits a directed motion of a particle in nonequilibrium steady states maintained by two heat baths. We measure heat transfer from each heat bath separately, and average them using a careful procedure that reveals the nature of the heat transfer associated with directed steps of the particle. Remarkably we find that steps are associated with nonvanishing heat transfer even in equilibrium, and there is a quantitative relation between this ``hidden heat transfer'' and the directed motion of the particle. This relation is clearly understood in terms of the ``principle of heat transfer enhancement'', which is expected to apply to a large class of highly nonequilibrium systems.