Multipolar quantum critical phenomena in Pr and Nd compounds under high pressures up to 20 GPa

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K03518
• 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: Hiroshima University
• Principal Investigator: Umeo Kazunori 広島大学, 自然科学研究支援開発センター, 准教授 (10223596)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 電気四極子秩序 / 超伝導 / 静水圧力 / 異方的圧力 / 反強磁性秩序 / 2チャンネル近藤効果

Outline of Final Research Achievements

Superconductivity in PrIr2Zn20 appears at Tc = 0.05 K in the presence of an antiferroquadrupolar order below TQ = 0.11 K. We have studied pressure dependences of Tc, TQ by using two pressure transmitting media: argon maintaining highly hydrostatic pressure and glycerol which solidifies above 5 GPa producing non-hydrostatic pressure. Upon applying P with argon up to 10.6 GPa, Tc hardly changes while TQ monotonically increases from 0.11 K to 0.23 K. With glycerol, however, TQ and Tc simultaneously fall below 0.04 K at 6.3 GPa. The contrasting results indicate that onsite quadrupolar fluctuations induce superconductivity in this compound.
The downward behavior in the resistivity of NdCo2Zn20 up to 13 GPa can be reproduced by the theoretical formula based on the two channel Kondo effect.

Free Research Field

低温高圧下における磁性

Academic Significance and Societal Importance of the Research Achievements

希土類プラセオジム（Pr）を含む化合物において、Prの電気四極子が空間整列した状態（電気四極子秩序）で超伝導が発現するには、電気四極子のゆらぎが必要不可欠であることを、世界で初めて実験的に立証した。この研究によって，これまでに発現機構が解明されていない特異な超伝導の機構解明につながり，さらに，新しい高温超伝導などの新規材料開発の指針を与える。