Real-space observation of orbital electrons in multipole ordered states

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K14010
• 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 (2023); Institute of Physical and Chemical Research (2022)
• Principal Investigator: Kitou Shunsuke 東京大学, 大学院新領域創成科学研究科, 助教 (20887327)
• Project Period (FY): 2022-04-01 – 2024-03-31
• Keywords: 電子軌道 / 放射光 / X線回折 / スピン-軌道相互作用

Outline of Final Research Achievements

In 4d, 5d, and 4f electron systems, the effects of relativistic spin-orbit interaction can manifest in their physical properties. As a result, the entanglement of spin and orbital degrees of freedom can reconstruct electron density, leading to the formation of multipole order. However, until now, there have been no examples of observing multipole order states, referred to as "hidden order," as electron density distributions in real space. In this study, by combining high-energy X-ray diffraction at the synchrotron facility SPring-8 with a core differential Fourier synthesis method developed by the applicant, we successfully achieved real-space observation of multipole order in pyrochlore-type oxides.

Free Research Field

構造物性

Academic Significance and Societal Importance of the Research Achievements

本課題を通じて、多極子状態を価電子密度分布として実空間観測する方法を確立することができた。この研究手法は、我が国が世界に誇るSPring-8放射光施設で得られる高エネルギーX線の性能を最大限に活かしたものであり、高い独創性と幅広い汎用性がある。今後、この手法を用いることで、多極子状態を構成する波動関数や相互作用の大きさを直接的に評価できるだけでなく、物質開発に対する設計指針や、量子多体系におけるエンタングルメント状態への情報提供が可能となるかもしれない。