Interplay between unusual superconducting critical field and magnetic correlation in Pauli-limited superconductors

2020 Fiscal Year Final Research Report

• Project/Area Number: 17K05529
• 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: Ibaraki University
• Principal Investigator: Yokoyama Makoto 茨城大学, 理工学研究科(理学野), 准教授 (70361285)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: 超伝導 / 磁気秩序 / 量子臨界現象

Outline of Final Research Achievements

It is known that in the Pauli-limited superconductor CeCoIn5, substituting In with Zn yields little change of superconducting upper critical field Hc2, although reduces superconducting transition temperature. The present research project revealed that this Hc2 feature is governed by antiferromagnetic quantum critical fluctuations (QCFs) via the Pauli-paramagnetic effect. In particular, we elucidated the antiferromagnetic order parameter responsible for the field-induced QCFs in CeCoIn5, which had been unidentified for a long time. This finding suggests that the Zn-doped CeCoIn5 provides a platform to investigate the interplay of the QCFs and unconventional superconductivity.

Free Research Field

物性物理

Academic Significance and Societal Importance of the Research Achievements

本研究では、CeCo(In1-xZnx)5 のHc2異常をもたらす背景には、パウリ常磁性効果を通じて強い反強磁性量子臨界揺らぎが重要な役割を果たしていることを解明した。この過程で、磁場誘起量子臨界揺らぎの原因となる秩序変数や、そのIsing的磁気異方性を明らかにした。エキゾチック超伝導体のプロトタイプであるCeCoIn5でのこれらの発見は、広く強相関電子系超伝導体において、異常な超伝導状態の発現には量子臨界揺らぎの寄与が不可欠であることを示唆するものである。本研究の成果によって、さらに今後の超伝導と量子臨界揺らぎに関する包括的な研究を推進していく契機となる。