Research Highlights

The unusual complexity of ferroelectric materials (FEMs) makes their fabrication, characterization, and modeling challenging. Unlike their magnetic counterparts, whose dynamic and transport properties whose physics are well understood through the magnon quasiparticles, FEMs and the corresponding “ferron” quasiparticle concept remain relatively unexplored.

“Theoretical work on the dynamics of FEMs often focuses on the harmonic regime of these materials,” explains Ping Tang, a member of an AIMR research team. “This practice neglects the non-linearity in the equations of motion unique to ferroelectric polarization, completely missing the ferron concept.”

In a 2022 article, Tang, Bauer et al. addressed this discrepancy by systematically including the anharmonicity in displacive FEMs to capture the elusive ferrons¹. Using the Landau-Ginzburg-Devonshire theory, the team calculated the static electric dipole carried by a ferron, analogous to the spin or magnetic moment carried by a magnon in magnetic materials.

Further, the identification of the ferron excitations that carry both heat and electric dipole currents opened the path to predicting FEM properties, including low-temperature pyroelectric and electrocaloric coefficients, the Peltier and Seebeck coefficients, field-dependent thermal conductivity, and ferron drag thermoelectricity in ferroelectric van der Waals heterostructures.

“Until recently, researchers have paid little attention to the dynamic transport properties of FEMs,” says Tang. “By producing the first descriptions of ferrons, we hope to kick-start the new field of ‘ferronics’ to close the gap with the magnetic materials’ head start.”

A future direction will involve collaboration with the National Institute for Materials Science in Tsukuba, aiming for further experimental observation of ferron excitations.

(Author: Patrick Han)