Study of novel quantum state in strongly correlated system with orbital degrees of freedom

2021 Fiscal Year Final Research Report

• Project/Area Number: 17H02920
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Condensed matter physics II
• Research Institution: Osaka University (2018-2021); Tokyo Institute of Technology (2017)
• Principal Investigator: Izawa Koichi 大阪大学, 基礎工学研究科, 教授 (90302637)
• Co-Investigator(Kenkyū-buntansha): 細井 優 大阪大学, 基礎工学研究科, 助教 (00824111) ; 町田 洋 東京工業大学, 理学院, 助教 (40514740)
• Project Period (FY): 2017-04-01 – 2022-03-31
• Keywords: 強相関電子系 / 多極子

Outline of Final Research Achievements

We have studied the low-temperature phase diagram of the Pr-based non-Kramers system based on the low-temperature transport measurements in high magnetic fields under pressures. We have revealed the presence of four novel electronic states, including quadrupole ordering and non-Fermi liquid (NFL) behavior originating from the quadrupolar Kondo effect, inherent to the multipolar degrees of freedom in PrRh2Zn20.
On the other hand, in PrT2Cd20(T=Rh, Pt) with weaker c-f hybridization, the NFL behavior has been observed, although quadrupole order has not. Thus, the c-f hybridization has governed the phase diagram, but the evolution of the phase diagram is different from the expectation from the Doniach picture.
The present results require a different/modified picture than the Doniach picture for a unified understanding of the phase diagram containing the various novel electronic states inherent to multipolar degrees of freedom.

Free Research Field

低温物理学

Academic Significance and Societal Importance of the Research Achievements

f電子を持つ希土類化合物やアクチノイド化合物で見られる磁気秩序や非フェルミ液体的挙動，非従来型超伝導といった物性物理学における極めて重要な現象の多くは，f電子のスピン自由度に由来し，ドニアック描像で概ね理解されてきた．それに対し，本研究で得られた系統的な結果が，ドニアック描像の予想とは異なることが示されたことにより，四極子自由度による物理を考える場合には，すでに標準的な考え方として浸透しているドニアック描像とは別の考え方が必要であることを強く示唆している．このことは，f電子系で見られる特異な現象の統一的理解だけでなく新奇物性の開拓にも重要な情報を与え，当該分野の進展への貢献が期待される．