Caloric Effects Owing to Elastic Coupling at Electronic Phase Transitions

All electronically driven phase transitions are coupled to local ionic displacements, sometimes as their principal manifestation (e.g. charge density waves, ferroelectrics) and sometimes as a side effect (e.g. magnetism, metal to insulator transitions).<br/>The coupling to the lattice induces elastic strain fields, which have intrinsic long-range interactions, which deform the metric of space and cannot be screened. When strain fields are produced as a secondary order parameter in phase transitions - as for example in ferroelectrics - this produces unexpected consequences for the dynamics of order parameter fluctuations.<br/>I will discuss the consequences of electro-strictive coupling in Mott insulators such as the nickelates¹ and phase change materials such as GeTe², and flexoelectric coupling for the so-called quantum paraelectrics such as strontium titanate³.<br/><br/>GG Guzmán-Verri, RT Brierley, PB Littlewood Nature 576 (7787), 429-432 (2019)<br/>SAJ Kimber, <i>et al.,</i> arXiv preprint arXiv:2202.05565<br/>GG Guzmán-Verri, CH Liang, PB Littlewood, arXiv preprint arXiv:2205.14171