Experimental
Demonstrations of New Theorems in Non-Equilibrium Thermodynamics
Research School of
Chemistry, The Australian National University
Thermodynamics is the study of the flow of heat between states and its transformation into work. Our understanding of thermodynamics is largely confined to equilibrium states. The field of nonequilibrium thermodynamics represents a simple-minded extension of the 19th century concepts of equilibrium thermodynamics to systems that are close to, or near equilibrium. Moreover, these traditional concepts are limited in application to large systems, referred to as the thermodynamic limit. However, in the last decade, two new theorems have been proposed to revolutionise the field of thermodynamics and its application to modern systems.
These new theorems
firstly, lift the restriction of the thermodynamic limit, allowing
thermo-dynamic concepts to be applied to small systems, and secondly,
characterise systems that may be far-from-equilibrium. The first of these
theorems, the Fluctuation Theorem (FT), generalises the Second Law of
Thermodynamics so that it applies to small systems, including those that evolve
far from equilibrium. The second, the Work Relation (WR), provides a method of
predicting equilibrium free energy differences from the experimental
trajectories of systems, including those that traverse far from-equilibrium
states. Both of these theorems are at odds with a traditional understanding of
19th century thermodynamics where equilibrium is central and the Second Law
inviolate. However these theorems are critical to the application of
thermodynamic concepts to systems of interest to scientists and engineers in
the 21st century. Both theorems, the FT and WR, embody concepts that are not
fully explored and are not necessarily accepted amongst scientists;
consequently, the practical theorems are not yet widely used. In this talk we
will describe the theorems in practitoners language, along with our optical
tweezers experiments that irrefutably demonstrate the theorems.