Exploration of novel strongly correlated electronic states by dopant adsorption on Mott insulators

2022 Fiscal Year Final Research Report

• Project/Area Number: 21K13872
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: The University of Tokyo
• Principal Investigator: HORIO MASAFUMI 東京大学, 物性研究所, 助教 (80897025)
• Project Period (FY): 2021-04-01 – 2023-03-31
• Keywords: モット転移 / 光電子分光 / 強相関電子系 / 表面吸着 / キャリアドープ

Outline of Final Research Achievements

In this research project, we explored novel Mott transitions by dopant adsorption on the surface of Mott insulators. In particular, we deposited alkali metals and C60 on Mott-insulating Ca2RuO4 and found, by observing the surface electronic states using photoemission spectroscopy, a metallic state which cannot be realized by carrier doping to the bulk of the sample. Furthermore, we extended the target to strongly correlated materials in general which do not accept carrier doping by chemical substitutions and/or where the influence of carrier doping remains unclear. It was found that, by alkali-metal dosing, that the metal-semimetal transition in Ca3Ru2O7 is suppressed and a new metallic state is realized. We also revealed that the antiferromagentic correaltion in the high-temperature superconductor (Pr,La,Ce)2CuO4 varies depending directly on the electron concentration.

Free Research Field

強相関電子系

Academic Significance and Societal Importance of the Research Achievements

固体にキャリアをドープする方法として、結晶中の元素の一部を価数の異なる元素で置換するという手法が広く用いられてきたが、イオン半径の違いにより元素置換が施せず、キャリアをドープできないような場合が多く存在した。本研究では、自由度の高い固体表面を土台にすることで、元素置換に依らない原子・分子表面吸着によりキャリアドープを実現し、それを表面敏感な光電子分光を用いて直接観測することで、固体内部では実現できないような新たな強相関金属状態を見出した。