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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 9: (Multi)ferroic States: From Fundamentals to Applications (IV)
KFM 9.2: Vortrag
Dienstag, 18. März 2025, 12:00–12:15, H9
Thermoelectricity from domain wall formation in a polar metal — •Feifan Wang1,2, Carl Romao1, and Manfred Fiebig1 — 1Dept. of Materials, ETH Zurich, Switzerland — 2Institute of Physics, Beijing 100190, China
Simultaneous optimization of the electronic and phononic properties of a thermoelectric material is essential to achieve a high thermoelectric performance. This has been realized in the polar metal compounds by making use of the high configurational entropy, Rashba effect and ferroelectric anharmonicity, tuned at the atomic level. What has been overlooked in this process is the role of macroscopic effect such as the role of domain and domain wall formation in further enhancing the thermoelectric performance. Using GeTe as a prototype, we show that microdomain formation determines the thermal conduction in the polar metal examined by the spatial correlation between the domain structure and the thermal conductivity. In particular, the thermal conductivity decreased by a factor of five following the appearance of the micro-sized antiparallel-aligned domains. Conductive force microscopy shows that the electrical conduction does not change in spite of the presence of domain discontinuities. This is in line with the band gap reduction and the electron--phonon decoupling from density-functional theory calculations. The direct visualization of the association between microdomain formation and thermal/electrical transport suggests the domain and domain wall engineering as a key ingredient in advancing polar-metal-based thermoelectrics.
Keywords: Polar metal; Thermoelectric; Domain wall; Nonlinear optics; Ferroelectric