Research on the mechanism of exotic superconductivity coupled with quantum critical fluctuations

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K03852
• 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: Ibaraki University
• Principal Investigator: Yokoyama Makoto 茨城大学, 理工学研究科(理学野), 教授 (70361285)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 超伝導 / 磁気秩序 / 量子臨界現象

Outline of Final Research Achievements

When Zn ions are doped into the exotic superconductor CeCoIn5, the superconducting transition temperature is suppressed, and two types of antiferromagnetic order are induced in the low and high magnetic-field regions. In contrast, magnetic quantum critical fluctuations occur when suppressing the superconducting transition temperature in the Ni-doped CeCoIn5. This study investigated the characteristics of the quantum critical fluctuations on the verge of these antiferromagnetic orders for the Zn- and Ni-doped alloys. It is found that the quantum critical point originating from the low-field antiferromagnetic order parameter coexists within the superconducting phase at zero magnetic fields, whereas the field-induced quantum critical point has a competitive relationship with the superconductivity.

Free Research Field

物性物理

Academic Significance and Societal Importance of the Research Achievements

本研究では、エキゾチック超伝導体CeCoIn5のZnおよびNi置換系において、2つの磁気的秩序変数に起因した量子臨界点およびその量子磁気揺らぎを発見した。これらは、CeCoIn5が示す異常超伝導物性と密接に関係していることを強く示唆する。CeCoIn5の超伝導物性については理論的・実験的研究の蓄積によって個々の異常物性の理解は進みつつある。今回の上記発見により、量子臨界現象を起源とした異常超伝導物性として系統的・包括的理解が進むことが期待できる。