Quantifying and minimizing dissipation in a non-equilibrium phase transition

TL;DR

This study measures and reduces dissipation during a non-equilibrium phase transition in a liquid crystal, confirming theoretical predictions and demonstrating a protocol to significantly lower energy loss.

Contribution

It provides the first experimental measurement of dissipation during a phase transition and introduces an automated method to optimize control protocols for minimal energy loss.

Findings

Dissipation scales with the Kibble-Zurek mechanism.

Automated optimization reduces dissipation by a factor of three.

Experimental results agree with theoretical predictions.

Abstract

In a finite-time continuous phase transition, topological defects emerge as the system undergoes spontaneous symmetry breaking. The Kibble-Zurek mechanism predicts how the defect density scales with the quench rate. During such processes, dissipation also arises as the system fails to adiabatically follow the control protocol near the critical point. Quantifying and minimizing this dissipation is fundamentally relevant to nonequilibrium thermodynamics and practically important for energy-efficient computing and devices. However, there are no prior experimental measurements of dissipation, or the optimization of control protocols to reduce it in many-body systems. In addition, it is an open question to what extent dissipation is correlated with the formation of defects. Here, we directly measure the dissipation generated during the voltage-driven Freedericksz transition of a liquid crystal with a sensitivity equivalent to a ~10 nanokelvin temperature rise. We observe Kibble-Zurek scaling of dissipation and its breakdown, both in quantitative agreement with existing theoretical works. We further implement a fully automated in-situ optimization approach that discovers more optimal driving protocols, reducing dissipation by a factor of three relative to a simple linear protocol.