Suppression of octapole order by tuning the dimensionality in Ce1-xLaxB6/SrB6 superlattices

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K05456
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Condensed matter physics II
• Research Institution: Osaka Prefecture University
• Principal Investigator: Shishido Hiroaki 大阪府立大学, 工学(系)研究科(研究院), 准教授 (80549585)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 強相関電子系 / 薄膜成長 / トポロジカル絶縁体

Outline of Final Research Achievements

I grew epitaxial thin films of rare-earth hexaborides by the molecular beam epitaxy method. Thin films grown on c-plane Si substrates at 1000 degrees Celsius. The [100] axis of rare-earth hexaboride epitaxial thin films is oriented to the [110] axis of Si substrates. Artificial superlattices in which a candidate of the topological insulator SmB6 and topologically trivial insulator SrB6 stacked alternately. At superlattices with 3-unit cell thick SmB6 layers, the resistivity increases logarithmically with decreasing temperature even below 3 K. The most plausible scenario is that reducing the SmB6 layer thickness increases the interaction between topological surface states at the interface between SmB6 and SrB6 and eventually the gap in the Dirac cone is opened.

Free Research Field

固体物理学

Academic Significance and Societal Importance of the Research Achievements

SmB6は近藤効果が効いている新しいタイプのトポロジカル絶縁体，近藤トポロジカル絶縁体の候補物質である．本研究ではSmB6とトポロジカルにトリビアルな絶縁体の超格子を作り，SmB6層の厚みを薄くすることで，表面電子状態間の相互作用を増大させた．トポロジカル絶縁体ならば，相互作用によりディラックコーンにギャップが開き，絶縁体的な振る舞いに移行することが期待される．SmB6の人工超格子では，SmB6層を薄くすることで，電気抵抗率の振る舞いが絶縁体的になることが確認された．これは，SmB6が近藤トポロジカル絶縁体であることを支持する結果である．