Enhancement of carrier mobility and development of superconducting properties in heavy pnictogen square net insulators

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K14532
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 29020:Thin film/surface and interfacial physical properties-related
• Research Institution: Tohoku University
• Principal Investigator: Kawasoko Hideyuki 東北大学, 理学研究科, 助教 (20757132)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 正方格子 / ニクトゲン / エピタキシャル薄膜 / 超伝導 / 高移動度

Outline of Final Research Achievements

In this study, we have synthesized La2O2Bi epitaxial thin films by multilayer solid phase epitaxy for the first time, achieved three times higher mobility than previously reported polycrystalline samples, and revealed the semimetallic nature of the La2O2Bi. We synthesized La2O2Sb epitaxial thin films by molecular beam epitaxy, and demonstrated that the Sb deficiency is the origin of the dramatic resistance reduction in La2O2Sb epitaxial thin films. As an unexpected result, rock-salt type LaSb and LaBi thin films were synthesized by multilayer solid phase epitaxy under high temperature conditions of nearly 1000°C. In addition, we found a c/a ratio dependence of the superconducting transition temperature, which is not limited to oxygen insertion, by applying various elemental substitutions to Y2O2Bi polycrystalline samples.

Free Research Field

固体化学

Academic Significance and Societal Importance of the Research Achievements

グラフェンの発見以降、単原子の原子層物質はハニカム格子系を中心としてさかんに研究されている。そうした中、本研究では、単原子正方格子層を含む層状物質La2O2Pn (Pn =Sb, Bi)のエピタキシャル薄膜の合成を実現し、電子物性を評価した。ハニカム格子系に肩を並べる成果とは言い難いが、単原子正方格子という新しい系を開拓できた点に学術的な意義がある。また、多層膜固相エピタキシー法によって、単原子正方格子物質だけではなく、岩塩構造のLaPnの薄膜合成も実現できたことから、蒸気圧の高い元素を含む物質の薄膜合成における多層膜固相エピタキシー法の有用性を示すことができた。