When a rubber band is quickly stretched, its temperature will increase. This strain-induced temperature change is known as the elastocaloric effect. Measuring the elastocaloric effect provides a new probe into the behavior of quantum materials characterized by the interplay of a rich variety of phenomena, such as orbital order, magnetism or superconductivity.

In a new study, Ikeda et al. present a new technique that allows for the precise determination of the elastocaloric effect, providing a high-resolution look at the change in entropy of a material as it is stretched. Co-author Matthias Ikeda said in contrast to other thermodynamic properties, the signatures of phase transitions in the elastocaloric effect could be measured against a small phononic background, even at higher temperatures.

In the study, the team applied a fast oscillating force to the iron-based material. A high enough frequency prevents heat from flowing in and out of the system.

“Under these adiabatic conditions, the entropy of the material does not change, and thus, the elastocaloric effect translates into a temperature oscillation, which can easily be measured,” Ikeda said.

The authors further showed their measurements contained little background signal and were proportional to transition features observed through heat capacity measurements, confirming the precision and accuracy of their technique. Finally, by varying the strain at multiple offsets, the authors showed they could trace the entropy landscape in multiple dimensions.

The study’s results could enable a better understanding of the behavior of quantum materials at both finite temperatures and absolute zero.

Source: “AC elastocaloric effect as a probe for thermodynamic signatures of continuous phase transitions,” by Matthias S. Ikeda, Joshua A. W. Straquadine, Alexander T. Hristov, Thanapat Worasaran, Johanna C. Palmstrom, Matthew Sorensen, Philip Walmsley, and Ian R. Fisher, Review of Scientific Instruments (2019). The article can be accessed at https://doi.org/10.1063/1.5099924.