2020 Fiscal Year Final Research Report

Search for novel physical properties in spin-orbit fluctuated systems

Research Project

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Project/Area Number	18K03543
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Multi-year Fund
Section	一般
Review Section	Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
Research Institution	Kagoshima University
Principal Investigator	Okuda Tetsuji 鹿児島大学, 理工学域工学系, 准教授 (20347082)
Co-Investigator(Kenkyū-buntansha)	梶本亮一国立研究開発法人日本原子力研究開発機構, 原子力科学研究部門 J－PARCセンター, 研究主幹 (30391254) 齋藤智彦東京理科大学, 理学部第一部応用物理学科, 教授 (30311129) 桑原英樹上智大学, 理工学部, 教授 (90306986)
Project Period (FY)	2018-04-01 – 2021-03-31
Keywords	強相関電子材料 / 二量体 / 電荷整列 / 熱電特性 / 擬ブルッカイト
Outline of Final Research Achievements	In this project, we searched for novel physical properties in chemically substituted pseudobrookite Ti3O5 with enhanced spin-orbit fluctuations. In the low temperature β phase of Ti3O5, a spin-singlet dimerization between the neighboring Ti3+ ions occurs with accompanying Ti3+/Ti4+ charge ordering. We succeeded in growth of the single crystals mixed with AlTi2O5 having the similar structure and found that the α, λ, and β phases sequentially appeared at room temperature with the change in the Al content and that the correlated conductive state where the dimer correlations strongly remained were realized even in the paramagnetic α and λ phases. Furthermore, we found unique magnetic properties and relatively good high-temperature thermoelectric properties, originating in the fluctuations of dimerization, near the phase boundary between the λ and β phases.
Free Research Field	物性実験
Academic Significance and Societal Importance of the Research Achievements	スピン一重項の二量体形成は一般的な量子現象であり、Ti3O5やTi4O7の低温での二量体形成は古くから知られていた。ところが、Ti3O5のλ相やTi4O7の中間相ではバイポーラ・スピン液体状態や異常コヒーレント状態などが提案されており、それらの磁気・電子状態は未解明のままであった。さらに、近年、理論や実験の進展に伴い、スピン・軌道整列が起源となる多量体形成が多くの物質で見出され、その物性研究が進展しつつある。以上の背景のもと、本課題で育成に成功した元素置換したTi3O5やTi2O3の単結晶での発見は、二量体物性の理解を深化させ、さらに、巨大熱電応答など新量子物性につながる重要なものと思われる。