Experimental determination of low-energy excited structures by electronic correlation and disorder

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K13882
• 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: Kyoto University
• Principal Investigator: Ootsuki Daiki 京都大学, 人間・環境学研究科, 助教 (80780957)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 強相関電子系 / アンダーソン局在 / 光電子分光 / １粒子スペクトル関数 / 遷移金属

Outline of Final Research Achievements

In this research project, we have directly observed the single-particle excitation spectra in systems where electron correlation and disorder coexist using photoelectron spectroscopy and worked to clarify the characteristic electronic structures induced by electron correlation and disorder. In particular, we have investigated the impurity effect in Ru oxides and semiconducting materials from the perspective of electronic states. In Ru oxides, we have successfully observed the band dispersion and determined the bulk and surface electronic structures. Furthermore, for the semiconducting materials, we have determined the localized level formed by the impurity substitution and discuss the effect to the electrical conductivity. During this research, we also discovered that the extremely low-density state is realized in vicinity of surface on the semiconducting materials.

Free Research Field

物性物理学

Academic Significance and Societal Importance of the Research Achievements

現実の物質では電子相関と乱れの効果が共存している。しかし、両者が顕著に異なる性質を示すことから取り扱いが困難であり、特に強相関電子系においてはほとんど理解が進んでいない。本研究では、多体電子相関と乱れの効果が共存する系において電子状態の直接観測から１粒子励起スペクトルを決定した。強相関電子系における我々の研究成果は、強相関電子系における不純物伝導の理解を深化させ、理論研究との更なる相乗効果をもたらすと考えられる。さらに不純物添加した半導体のフェルミ準位近傍の電子状態の決定は、熱電材料の性能向上や不純物添加による強磁性などの機能性の付与など更なる展開も期待される。