Coupling between unconventional quantum-critical fluctuations and superconductivity in layered superconductors

2017 Fiscal Year Final Research Report

• Project/Area Number: 15H03693
• 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: Tokyo Metropolitan University
• Principal Investigator: Aoki Yuji 首都大学東京, 理工学研究科, 教授 (20231772)
• Co-Investigator(Renkei-kenkyūsha): MATSUDA Tatsuma 首都大学東京, 理工学研究科, 准教授 (30370472) ; HIGASHINAKA Ryuji 首都大学東京, 理工学研究科, 助教 (30435672) ; MIZUGUCHI Yoshikazu 首都大学東京, 理工学研究科, 准教授 (50609865) ; HIGEMOTO Wataru 独立行政法人日本原子力研究開発機構, 先端基礎研究センター, 研究主幹 (90291103)
• Project Period (FY): 2015-04-01 – 2018-03-31
• Keywords: BiS2層状超伝導体 / 量子臨界的挙動 / 空間反転対称性の破れ / ファンデルワールス層状物質 / 純良単結晶育成

Outline of Final Research Achievements

BiS2-based superconductors are pseudo-2D materials consisting of alternating stacks of block layers, which possess rare-earth ions, and BiS2 conducting layers. We have grown high-quality single crystals with controlled carrier doping for each rare-earth elements, and have studied the anisotropies of 4f-electron magnetism and electronic conduction as well as the coupling between the two.
We have found at low temperatures that unconventional quantum critical behaviors (logT divergence in the specific heat) appearing in Ce-based materials in a nonmetallic state and heavy-fermion behaviors in Nd-based materials. In the superconducting state, we have found anomalous behaviors of the upper critical field Hc2, i.e., largely enhanced Hc2 caused by the breaking of the local inversion symmetry at the electronically active BiS2 bilayers and its anomalous temperature dependence suggesting different gap sizes on the Fermi surface.

Free Research Field

電子物性