Study for Mott transition and pressure induced superconductivity in the iron-based ladder compounds using ac-specific measurements

2020 Fiscal Year Final Research Report

• Project/Area Number: 17K05531
• 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: The University of Tokyo
• Principal Investigator: yamauchi touru 東京大学, 物性研究所, 技術専門員 (10422445)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: 高圧下交流比熱測定 / 圧力誘起絶縁体超伝導転移

Outline of Final Research Achievements

Calorimeters were constructed using BaFe2S3 and beta-Na0.33V2O5, and AC specific heat measurements under high pressure were carried out over a wide temperature range at around the critical pressure, where the insulating phase transitions to the superconducting phase. In the former case, the specific heat enhancement was observed in the critical pressure region where the superconducting phase and the Mott insulating phase are adjacent, and this trend was also observed at temperatures higher than the superconducting transition temperature. This is not explained by the crossover phenomenon proposed in the orbital-selective model, but indicates that there is some kind of transition. In the latter case, where there is a clear symmetry-breaking phase transition, the specific heat enhancement anomaly near the critical pressure was also observed. Furthermore, the charge-ordering and superconducting transitions were also clearly observed when the temperature was swept.

Free Research Field

高圧物性

Academic Significance and Societal Importance of the Research Achievements

測定技術開発を行い成功することは，シンプルに意義がある．強相関電子系として典型的な絶縁相基底状態を持つ系が，乱雑さを加えない方法で，超伝導相に転移をする場合，その背景で如何なる変化が起こっているかは，銅酸化物高温超伝導体発見以来の現代物性物理学上の中心的課題の一つである．この課題への実現可能なアプローチとして，15GPa程度の範囲で圧力誘起超伝導相探索に威力を発揮してきたキュービックアンビル型圧力装置での交流比熱測定を志向した．比熱はエントロピーを介して，ボルツマン関係式で系の状態数に直接結びついている物理量なので，圧力誘起される強相関電子系金属の物理学を議論する上で強力な測定法である．