Dependence of efficiency on the nonlinear nature of a nanomachine

Abstract

We establish the power output and efficiency of a single-particle nanomachine whose characteristic component is a nonlinear potential $U(r)\ensuremath{\propto}{|r|}^{\ensuremath{\alpha}}$. We do so by considering multi-temperature ``elliptic'' and Carnot-like cycles. In both protocols we verify the linear case $\ensuremath{\alpha}=2$ corresponds to a threshold situation. In the former, it establishes the transition from a machine behavior---wherefrom we can extract work---to a refrigerator performance. Last but not least, a closer look at the isentropic lines of these systems sets clear parameter value limitations to the definition of a Carnot cycle using such type of mechanical system. An observation that goes beyond standard thermodynamic conditions, where the existence of a Carnot cycle must be material independent.