Anomalous acoustic phonons as the physical mechanism behind the adiabatic barocaloric effect on graphene

A graphene sheet is able to either heat up or cool down due to a mechanical strain: this is the adiabatic barocaloric effect. In order to understand the physical mechanism behind this effect, we have explored the adiabatic temperature change of the graphene and, for this purpose, we considered two contributions to the total entropy: a lattice entropy (depending on the transversal, longitudinal and anomalous out-of-plane acoustic phonons) and a strain entropy. We found that the adiabatic barocaloric effect only depends on the strain energy and the anomalous acoustic phonons, without terms due to the transversal and longitudinal acoustic phonons.