Dresden 2026 – scientific programme
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FM: Fachverband Funktionsmaterialien
FM 22: Focus Session: Materials Discovery III – New materials and functionalities by general principles
FM 22.9: Talk
Friday, March 13, 2026, 12:00–12:15, BEY/0138
Interplay between Lattice Dynamics and Free Electrons in Polar Metals: A Chemical-Bonding Perspective — •Hiroto Kikuchi1, Suguru Yoshida1, Hiroshi Takatsu1, Kantaro Murayama1, Peter Lemmens2, and Hiroshi Kageyama1 — 1Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan — 2Institute for Condensed Matter Physics, Technische Universitat Braunschweig; Braunschweig 38106, Germany
Polar-nonpolar (P-NP) transitions in metals such as LiOsO3 show that polar order can coexist with metallicity, defining "polar metals" as a new class of quantum materials. However, the microscopic mechanism remains under debate, with competing scenarios invoking electron-phonon coupling and coordination bonding.
We recently found that metallic LiReO3, isostructural with LiOsO3 and adopting the LiNbO3-type structure, undergoes a P-NP structural transition at Ts = 170 K. Unlike the second-order transition in LiOsO3, LiReO3 shows thermal hysteresis and strong lattice softening, indicating enhanced fluctuations between polar and nonpolar phases.
We investigated Raman scattering across Ts, combined with phonon calculations and crystal orbital Hamilton population (COHP) analysis, and reveals strongly redshifted LiO6-related optical phonons in LiReO3 compared with LiOsO3. These results, supported by computed force constants and bond strengths, provide a unified picture of phonon softening and polar stability in metallic LiReO3.
Keywords: Polar matal; Functional materials; Oxides