Fabrication of Wyle semimetal by topological insulator/insulator artificial superlattice

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K03751
• 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: 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): 2019-04-01 – 2022-03-31
• Keywords: ワイル半金属 / 近藤トポロジカル絶縁体 / 人工超格子 / SmB6

Outline of Final Research Achievements

We applied an electric field up to 5 V to the SmB6 ultrathin films, which is known as a topological Kondo insulator, by using an ionic liquid. And then we measured temperature dependence of the electrical resistivity down to 2 K under electric fields. Resulting no clear difference was observed from that without electrical field up to 5 V.
We succeeded in fabricating artificial superlattices with stacking layers of CaB6, SmB6, and SrB6 on a Si substrate. Temperature dependence of the electrical resistivity of the SrB6/SmB6/CaB6 artificial superlattices was measured down to 2 K. The electrical resistivity increased with decreasing temperatures, starts to saturate below 10 K. We also observed a weak positive magnetoresistance at 2 K, while the SmB6 thin films exhibits weak negative magnetoresistance.

Free Research Field

強相関電子系

Academic Significance and Societal Importance of the Research Achievements

トポロジカル絶縁体はバルクには絶縁体であるが表面にだけ伝導電子が存在する．SmB6はそのようなトポロジカル絶縁体の一種である．トポロジカル絶縁体のSmB6の薄膜を作製し，電場を印可する，同じ結晶構造を取るCaB6, SrB6とSmB6を順番に積層する，の２通りの方法でSmB6の空間反転対称性を破ることを試みた．ここで空間反転対称性を破るとは，電場方向あるいは積層方向に極性を付けることを意味する．これにより高い移動度で電荷を運べる準粒子を実現できる可能性がある．本研究ではその実現可能性について検証を行った．