Search for a Kondo semiconducting state near the quantum critical point under high pressure

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K18737
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 13:Condensed matter physics and related fields
• Research Institution: Hiroshima University
• Principal Investigator: Matsumura Takeshi 広島大学, 先進理工系科学研究科(先), 教授 (00312546)
• Co-Investigator(Kenkyū-buntansha): 梅尾 和則 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): 2018-06-29 – 2021-03-31
• Keywords: 磁性 / 電気伝導 / 量子臨界現象 / 圧力

Outline of Final Research Achievements

We have studied the electronic properties of CeS, which has recently been expected to realize a Kondo insulator state under high pressure due to an increase in c-f hybridization, starting from a normal Kondo metal. We measured the electrical resistivity and Hall effect up to pressures above the critical point Pc. Although a strong anomaly was observed in resistivity reminiscent of a semiconducting state, the Hall effect did not exhibit a semiconducting behavior, indicating that the anomalous increase in resistivity is caused by a mechanism different from the energy gap formation at the Fermi level. Another finding in this research from which we expect future progress is on TmTe, which exhibit an insulator-to-metal transition with a simultaneous appearance of a ferromagnetic order. We found an anomalous increase in magnetic susceptibility around the critical pressure which is reminiscent of a precursor of the ferromagnetism.

Free Research Field

強相関電子系物理

Academic Significance and Societal Importance of the Research Achievements

物質は一般に金属か絶縁体のどちらかに分類されるが，その境界領域がどうなっているかは実はまだ謎が多い．金属に圧力をかけることで電子状態を変化させ，絶縁体に移り変わる過程，あるいは絶縁体から金属に変わる過程が詳細に観察できれば，その謎に迫ることができる．しかし，その様相は多彩である．本研究では原子に局在して磁性を担う電子も電気伝導性の変化に関与する現象のいくつかを調べた．圧力下で電子間の相互作用が変化することで，伝導電子の散乱状態が変わったり，また，電子が原子に局在した状態から原子間を動き回る状態に変化することでスピンがそろう強磁性に変化する現象などを詳細に調べた．