2025-08-05 九州大学
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図：常圧下のイットリウム金属は原子1個に対して、最大で3つの水素原子を吸蔵する。その二水素化物(YH2)は面心立方構造をとる。さらに水素が取り込まれ三水素化物(YH3)になると六方細密構造へ構造変化することが知られている。このYH2からYH3への水素吸蔵過程で金属－絶縁体転移が生じる。 オレンジ色の球がイットリウム金属、青色の球が水素を示す。
＜関連情報＞
- https://www.kyushu-u.ac.jp/ja/researches/view/1310
- https://www.kyushu-u.ac.jp/f/62804/25_0805_01.pdf
- https://pubs.aip.org/aip/ltp/article-abstract/51/7/870/3351216/In-situ-investigation-of-electronic-properties-in
点接触分光法を用いたイットリウム水和物の電子的性質のin situ調査 In situ investigation of electronic properties in yttrium hydride using point-contact spectroscopy
Kazuki Miyakawa;Zizhou Tai;Hiroki Takata;Taishi Yamaguchi;Masanobu Shiga;Yuji Inagaki;Tatsuya Kawae
Low Temperature Physics Published:July 01 2025
DOI:https://doi.org/10.1063/10.0036932
We report an in situ investigation of the electronic properties of yttrium hydride nanocontacts using point-contact spectroscopy (PCS), in which hydrogen (H) atoms were absorbed at T ≈ 16 K. The yttrium (Y) nanocontact was prepared by a mechanically controllable break junction technique at T ≈ 20 K, which prevents surface contamination and oxidation. For pure Y nanocontact, the differential conductance (dI/dV) spectrum exhibits an upward convex signal. When a small bias voltage is applied between the nanocontacts immersed in liquid H2, the dI/dV spectra change significantly due to H absorption in the nanocontacts. At an applied voltage of 350 mV, a V-shaped anomaly appears around zero bias in the dI/dV spectra. Moreover, the V-shaped anomaly becomes more pronounced as the temperature decreases, suggesting that the Y hydride nanocontact undergoes a transition to an insulating state upon hydrogenation. By comparing these results with the PCS spectra in Y hydride nanocontacts with the H concentrations of x = 2 and 3 measured at room temperatures, we conclude that the evolution of the spectra from a Y-metallic signal to a V-shaped feature is likely caused by a metal-insulator transition due to the phase transformation from YH2 to YH3.
