Elucidation of the origin of Anderson localization and exploration of superconductivity by controlling it in electron-correlated oxides

2023 Fiscal Year Final Research Report

• Project/Area Number: 20H02704
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 32020:Functional solid state chemistry-related
• Research Institution: Tokyo Metropolitan University (2022-2023); Tohoku University (2020-2021)
• Principal Investigator: Oka Daichi 東京都立大学, 理学研究科, 准教授 (20756514)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: アンダーソン局在 / 金属絶縁体転移 / 酸化物 / 酸窒化物 / エピタキシー / 複合アニオン / 超伝導

Outline of Final Research Achievements

We investigated the factors inducing the metal-insulator transition due to electron localization in electron-correlated conductive oxides, such as Nb-based oxides and oxynitrides, V-based layered oxides, Ru oxides, and rare-earth monoxides. As a result, we found that the disorder of the anion arrangement can be more significant than the Coulomb interaction between electrons, and that the dimensionality-induced metal-insulator transition appears by reducing the conductive layer or film thickness, but at the same time, the emergence of weak localization is determined by the interlayer interaction. We also found that the expansion of the orbital distribution leads to improved electrical conductivity. In rare-earth monoxides, the mobility of the itinerant 5d electrons changes depending on the number of the localized 4f electrons, and superconducting heterostructures were successfully fabricated.

Free Research Field

固体化学

Academic Significance and Societal Importance of the Research Achievements

本研究では電子相関系酸化物においてアニオン配列、層構造、格子歪み、膜厚、軌道分布の大きさといった要素が電子局在を引き起こす具体的な条件を実験的に検証することができ、これらのパラメータの制御方法が開発された。また、本研究では多様な酸化物を高品質なエピタキシャル薄膜として合成するための合成手法開発という面でも多様な手法を見出すことができ、理論的に高温超伝導を発現すると期待される層状酸化物のエピタキシャル合成も可能となった。これらの知見や技術は、今後、超伝導体をはじめとする導電性材料の開発に活用できると期待される。