Unattainability of Carnot efficiency in the Brownian heat engine

Abstract

We discuss the reversibility of the Brownian heat engine. We perform an asymptotic analysis of the Kramers equation on a Buttiker-Landauer system and show quantitatively that Carnot efficiency is unattainable even in the fully overdamped limit. The unattainability is attributed to inevitable irreversible heat flow over the temperature boundary.