[17p-A408-1~14] 6.3 Oxide electronics

[17p-A408-12] Metal-Insulator Transitions and Rattling Motions in β-Pyrochlore-Type Oxides

〇Takuto Soma¹, Kohei Yoshimatsu¹, Koji Horiba², Hiroshi Kumigashira², Akira Ohtomo¹ (1.Tokyo Tech., Dept. Chem. Sci. Eng., 2.KEK-PF)

Keywords:metal-insulator transition, pyrochlore, rattling

A group of substances with a large cage structure within the crystal structure is called clathrate compounds, and it is known that the cations enclosed in the cage exhibit anharmonic thermal vibrations (rattling motion). Therefore, there have been many attempts to apply such a group of materials to thermoelectric conversion materials. We have found that rattling motion freezing and charge disproportionation of Cs⁺ cations occur simultaneously around the metal-insulator transition (MIT) temperature in β-pyrochlore-type CsW₂O₆, a type of clathrate compound. In this study, we have investigated whether the same phenomenon occurs in MIT with hole-doping and to directly elucidate an relationships between the itinerancy of electrons and rattling motion of cations.