Pressure-Induced Superconductivity in Polar Compounds

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K14396
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
• Research Institution: Tohoku University
• Principal Investigator: Aoyama Takuya 東北大学, 理学研究科, 助教 (80757261)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 鉄系超伝導 / 軌道秩序 / ダイヤモンドアンビルセル

Outline of Final Research Achievements

In this study, we focused on the pressure-induced superconducting phase of BaFe2Se3, an iron-based ladder compound with a polar structure, and investigated the electrical resistivity and magnetotransport properties under pressure. We found that the polar structure caused by orbital ordering is suppressed by the application of pressure of about 4 GPa, and that the normal phase near the pressure-induced superconducting phase exhibits hole-dominant electronic conduction. In addition, we have measured the electrical resistivity, magnetization, optical conductivity, and neutron diffraction of BaFe2(S1-xSex)3, and found that an orbital state flop occurs around x = 0.23. Furthermore, we succeeded in synthesizing BaFe2(S1-xTex)3 as a new material system.

Free Research Field

強相関電子物性

Academic Significance and Societal Importance of the Research Achievements

鉄系超伝導体においては電子相関効果と多軌道性が重要なキーワードと認識されている．一方で鉄系超伝導体の母体は金属であるため，電子相関効果が超伝導相に与える影響は明らかでなかった．本研究で対象とする梯子型鉄系化合物は結晶構造の低次元性に起因して母体がモット絶縁体である．本研究では圧力印加および組成制御を通じたバンド幅制御によってモット絶縁体相から金属絶縁体転移・超伝導相へとアプローチすることで，鉄系超伝導体の電子相図に対して電子相関効果が与える影響を調べた．その結果，より強相関側においては，直交した軌道配列がより安定になることを明らかにした．