Band-filling control of topological semimetals having a 2D square lattice structure

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K03472
• 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: Okayama University
• Principal Investigator: KONDO Ryusuke 岡山大学, 環境生命自然科学学域, 准教授 (60302824)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: トポロジカル半金属 / 正四角格子 / 価数制御 / ディラック電子 / 価数制御 / 電荷密度波

Outline of Final Research Achievements

A sample preparation method for the filling control of the Ln(Sb, Bi)Te system was developed and applied to the square-net topological semimetal system with Ln = La. In the LaSbTe system, charge density wave (CDW) phases were stabilized in the Te-rich region, as reported previously. In the Sb-rich region, however, an unreported crystal structure with double periodicity along its stacking axis was found. In this structure, the square lattice is deformed into a characteristic kite shape. In the LaBiTe system, which was developed to investigate the effect of spin-orbit coupling interaction, square net structures were preserved across the entire range of compositions for which single-crystalline samples were obtained. Additionally, CDW phases appeared in some of these samples. These results indicate that our method is suitable for precise filling control of the Ln(Sb, Bi)Te system.

Free Research Field

物性物理学

Academic Significance and Societal Importance of the Research Achievements

トポロジカル物質は，その内部にトポロジカルな電子構造に基づく仮想磁場を有する物質であり，次世代デバイスの基幹材料として期待され，開発が進められている．しかし，この性質を発現させるためには，仮想磁場を与える電子構造の付近にフェルミ準位を合わせることが必要となるが，この条件を自然に満たす物質は多くない．これまでにトポロジカルな電子構造をもつ物質は数多く報告されているが，実際にバルクとしてその性質を発現出来ていない物質が殆どである．本研究は，これに属する物質系でのトポロジカル物性の発現を目指すためには重要な実験技術である価数制御法を開発したものであり，学術的にも重要な意味を持つ．