Exploration of exotic properties in chalcogenide thin films grown by topotactic reactions

2022 Fiscal Year Final Research Report

• Project/Area Number: 20H01847
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: Tohoku University
• Principal Investigator: Nakayama Kosuke 東北大学, 理学研究科, 助教 (40583547)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: カルコゲナイド / 原子層薄膜 / トポタクティック反応 / 角度分解光電子分光 / 電子状態

Outline of Final Research Achievements

We have developed a novel method to obtain chalcogenide thin films by utilizing a topotactic reaction combined with a molecular beam epitaxy (MBE). This method is particularly useful for the growth of sulfur-based thin films which is generally difficult by MBE only, as we have demonstrated a successful topotactic conversion of iron-based high-temperature superconductors, topological insulators, and transition metal dichalcogenides. By performing high-resolution angle-resolved photoemission spectroscopy, we have revealed the electronic states and physical properties of the obtained thin films and related compounds. For instance, we have found signatures of exotic quantum states such as pure electronic nematic states without involving a structural phase transition in iron-based high-temperature superconductors and charge density waves originating from higher-order Fermi surface nesting in transition metal chalcogenides.

Free Research Field

光電子固体物性

Academic Significance and Societal Importance of the Research Achievements

本研究では、MBE法とトポタクティック反応法を組み合わせた新しい手法を開発し、これまでMBE法単独では困難とされていた硫化物薄膜の作製に成功した。カルコゲナイドは変化に富んだ膨大な数が存在し、基礎から応用まで広範な分野で先端材料として盛んに利用されている。本研究において鉄系高温超伝導体やトポロジカル絶縁体、遷移金属ダイカルコゲナイドなどで有用性を実証したように、トポタクティック法を用いた新手法は様々なカルコゲナイドに広く適用できることから、カルコゲナイド薄膜の作製や物性研究の新基軸になると期待される。