Okamoto Yoshihiko, Amano Haruki, Katayama Naoyuki, Sawa Hiroshi, Niki Kenta, Mitoka Rikuto, Harima Hisatomo, Hasegawa Takumi, Ogita Norio, Tanaka Yu, Takigawa Masashi, Yokoyama Yasunori, Takehana Kanji, Imanaka Yasutaka, Nakamura Yuto, Kishida Hideo, Takenaka Koshi
Department of Applied Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan.
Department of Physics, Kobe University, Rokkodai 1-1, Nada-ku, Kobe, 657-8501, Japan.
Nat Commun. 2020 Jun 19;11(1):3144. doi: 10.1038/s41467-020-16873-7.
Since the discovery of the Verwey transition in magnetite, transition metal compounds with pyrochlore structures have been intensively studied as a platform for realizing remarkable electronic phase transitions. We report on a phase transition that preserves the cubic symmetry of the β-pyrochlore oxide CsWO, where each of W 5d electrons are confined in regular-triangle W trimers. This trimer formation represents the self-organization of 5d electrons, which can be resolved into a charge order satisfying the Anderson condition in a nontrivial way, orbital order caused by the distortion of WO octahedra, and the formation of a spin-singlet pair in a regular-triangle trimer. An electronic instability due to the unusual three-dimensional nesting of Fermi surfaces and the strong correlations of the 5d electrons characteristic of the pyrochlore oxides are both likely to play important roles in this charge-orbital-spin coupled phenomenon.
自从在磁铁矿中发现韦尔韦转变以来，具有焦绿石结构的过渡金属化合物作为实现显著电子相变的平台受到了广泛研究。我们报道了一种保持β-焦绿石氧化物CsWO立方对称性的相变，其中每个W 5d电子都被限制在规则三角形的W三聚体中。这种三聚体的形成代表了5d电子的自组织，它可以以一种非平凡的方式分解为满足安德森条件的电荷序、由WO八面体畸变引起的轨道序以及规则三角形三聚体中自旋单重态对的形成。由于费米面不寻常的三维嵌套以及焦绿石氧化物特有的5d电子的强关联导致的电子不稳定性，都可能在这种电荷-轨道-自旋耦合现象中发挥重要作用。
