The FFLO modulation vector observation using transport measurements in organic superconductors.

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K14400
• 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: SUGIURA Shiori 東北大学, 金属材料研究所, 助教 (20869052)
• Project Period (FY): 2020-04-01 – 2022-03-31
• Keywords: 超伝導 / 有機伝導体 / 強磁場 / 低温 / FFLO超伝導

Outline of Final Research Achievements

Anisotropic superconductors have attracted a lot of interest. When superconductivity is in the clean limit and the orbital effect is strongly quenched, a novel superconducting phase, Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase is theoretically predicted, which can be stabilized above the Pauli limit. In this study, we focused on the stability of the FFLO phase in the organic superconductors. Characteristic corrugations in the field dependence of the interlayer resistance in the superconducting phase were observed at any in-plane field directions. The features were ascribed to the commensurability (CM) effect between the Josephson vortex lattice and the periodic nodal structure of the superconducting gap in the FFLO phase. The CM effect was observed in a similar field region for various in-plane field directions, in spite of the anisotropic nature of the Fermi surface. The results clearly showed that the FFLO phase stability is insensitive to the in-plane field directions.

Free Research Field

低温強磁場物性

Academic Significance and Societal Importance of the Research Achievements

エキゾチック超伝導の外場に対する安定性の理解は超伝導の実用に向けて欠かせない。中でも磁場に対して強固なFFLO超伝導研究では、FFLO状態が限定的な環境下において発現する為、表面測定を用いた強磁場超伝導の秩序変数の直接観測が難しく、FFLO状態を決定付けるqベクトルの観測という重要課題が残されてきた。本研究では、qベクトルによってもたらされるノード構造を超伝導渦糸ダイナミクスから間接的に観測する事に成功した。有機超伝導体におけるqベクトルの面内異方性にまで言及した実験結果は本研究が初めてであり、この結果によって強磁場超伝導状態の安定性に関する理論的・実験的研究が更に前進する事が期待できる。