Experimental Evidence for a Polarization Current via its Peltier Effect

Ferroelectric materials (FEs) exhibit long-range dipolar order arising from the displacement of oppositely charged ions, enabling coupling between polarization and heat flow. Analogous to ferromagnets—where magnetic moments generate spin currents—FEs possess electric dipoles (p), polarization (P), and polarization currents (jₚ) carried by ferrons, the polarization counterparts of magnons. Early experimental work by Trepakov et al. [1] demonstrated a temperature difference across PMN capacitors during charging and discharging, attributed to a dielectric Peltier effect. Following the theoretical framework of Bauer et al. [2] and Wooten et al. [3], this work extends that concept to modern relaxor ferroelectrics (RFEs) with improved experimental control. Gold-coated 0.67Pb[Mg_1/3Nb_2/3]O₃-0.33PbTiO₃ (PMN-33PT) single crystals were subjected to AC electric fields along [001], and differential thermocouples measured temperature variations across electrodes under vacuum. The analysis follows Onsager relations for coupled polarization and heat transport, –j_P=σ▽E–Sσ▽T and j_Q=σ∏▽E–κ▽T, where ∏ is the polarization Peltier coefficient, σ the polarization conductivity, S the polarization Seebeck coefficient, and κ the thermal conductivity. With no applied heat flux ( j_Q=0), the equations simplify to ▽T=σΠ▽E/κ. In this regime, an applied electric field induces localized heat exchange at the metal/FE interface, analogous to the classical thermoelectric Peltier effect. Analytical modeling and frequency-sweep measurements show |ΔT| ∝ ω⁻¹ᐟ² with ω=D/2L² and D=κ/ρC. The observed temperature modulation under an AC field provides experimental evidence that polarization dynamics can induce measurable heat exchange in RFEs, supporting the existence of a polarization current. This polarization-Peltier signal can be taken as evidence for the existence of a thermally-driven polarization flux, like the spin-Peltier effect is one for spin fluxes.

[1] V. A. Trepakov et al., Europhys. Lett. 21, 891 (1993)

[2] G. E. W. Bauer et al., Phys. Rev. Lett. 126, 187603 (2021)

[3] B. L. Wooten et al., Sci. Adv. 9, eadd7194 (2023)