Generalized Clausius inequalities in a nonequilibrium cold-atom system

Thermodynamic inequalities, such as the Clausius inequality, characterize the direction of nonequilibrium processes. However, the latter result presupposes a system coupled to a heat bath that drives it to a thermal state. Far from equilibrium, the Clausius inequality can be generalized using information-theoretic quantities. For initially isolated systems that are moved from an equilibrium state by a dissipative heat exchange, the generalized Clausius inequality is predicted to be reversed. We here experimentally investigate the nonequilibrium thermodynamics of an initially isolated dilute gas of ultracold Cesium atoms that can be either thermalized or pushed out of equilibrium by means of laser cooling techniques. We determine in both cases the phase-space dynamics by tracing the evolution with position-resolved fluorescence imaging, from which we evaluate all relevant thermodynamic quantities. We confirm the validity of the generalized Clausius inequality for the first process and of the reversed generalized Clausius inequality for the second transformation. The Clausius inequality is a way of analysing the entropy of a given process and its routes can be found in the second law of thermodynamics. Here, the authors study the non-equilibrium thermodynamics of an ultracold atomic gas in order to confirm the validity of two generalized Clausius inequalities and provide insight into the processes of thermodynamic inequalities and nonequilibrium processes.

Automated summary

Thermodynamic inequalities, such as the Clausius inequality, characterize the direction of nonequilibrium processes. In this study, the authors experimentally investigate the nonequilibrium thermodynamics of an initially isolated dilute gas of ultracold Cesium atoms to confirm the validity of two generalized Clausius inequalities.