Topological Superconductivity in Chemically-Doped Nodal-Ring Semimetal

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K21846
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 13:Condensed matter physics and related fields
• Research Institution: Nagoya University
• Principal Investigator: Okamoto Yoshihiko 名古屋大学, 工学研究科, 准教授 (90435636)
• Project Period (FY): 2019-06-28 – 2021-03-31
• Keywords: 超伝導 / トポロジカル物性 / ノーダルリング半金属 / トポロジカル超伝導

Outline of Final Research Achievements

We aimed to find topological superconductivity in nodal-ring materials, where electronic bands cross on a ring at around the Fermi energy in the momentum space. We prepared CaAgP single crystals substituted by various elements and measured their physical properties. As a result, superconducting transitions at around 1.5 K were found in the Pd-doped CaAgP single crystals. Since the Pd-doped single crystals have electron carriers with very high mobility, the correlation between the topological surface state caused by the nodal ring and observed superconductivity is interesting. We also found that Nb2Pd3Te5 and chemically substituted Ta2Pd3Te5 show bulk superconducting transitions at 2-4 K. The relationship between spin Hall insulator, excitonic insulator, and superconductivity in this system might be interesting.

Free Research Field

物性物理学、固体化学

Academic Significance and Societal Importance of the Research Achievements

本研究におけるPd置換したCaAgPにおける超伝導の発見は、これまでにないノーダルリング系ならではのトポロジカル物性の実験的な確立や、実験可能なトポロジカル超伝導の新候補物質の実現に繋がりうる成果であり、物性物理の基礎学理の観点から学術的意義を有する。また、元素置換したTa2Pd3Te5とNb2Pd3Te5は励起子絶縁体やスピンホール絶縁体に関連がある物質系で発見された新超伝導体である。これらの特異な物理現象と超伝導の関係を明らかにし得る格好の系といえ、こちらも物性物理の基礎学理の観点から十分な学術的な意義を有すると考える。