Towards a fully electromagnetic control of the heat flux*

The development of phononics, the discipline that investigates phonon transport and aims at engineering devices with the same functionalities as electronic or photonic ones, has been hindered by the inherently challenging nature of phonon manipulation.

Here, we demonstrate theoretically a fully electric control of the phonon flux, which can be continuously modulated by an externally applied electric field in PbTiO₃, a prototypical ferroelectric perovskite, revealing the mechanisms by which experimentally accessible fields can be used to tune the thermal conductivity by as much as 50% at room temperature. Additionally, we show how, by imposing epitaxial strain, it is possible to achieve a giant electrophononic response, i.e., the dependence of the lattice thermal conductivity on external electric fields. Specifically, we show that tensile biaxial strain can be used to drive the system to a regime where the electrical polarization can be effortlessly rotated and thus yield giant electrophononic responses that are at least one order of magnitude larger than in the unstrained system. These results derive directly from the almost divergent behavior of the electrical susceptibility at those critical strains that drive the polarization on the verge of a spontaneous rotation.

These ideas are then applied to magnetic materials, where the lattice structure, and thus the thermal conductivity, can be manipulated via external magnetic fields. In particular, we predict the existence of large magnetophononic effects in FeRh, a material that undergoes a metamagnetic phase transition near room temperature

These findings open the way to a fully-electromagnetic control of phonon transport that can be exploited for the design of thermal transistors and pave the way to signal processing with phonons