Field-temperature phase-diagram of a high quality ruthenate superconductor

2022 Fiscal Year Final Research Report

• Project/Area Number: 18K04715
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 26020:Inorganic materials and properties-related
• Research Institution: National Institute for Materials Science
• Principal Investigator: KIKUGAWA Naoki 国立研究開発法人物質・材料研究機構, エネルギー・環境材料研究拠点, 主幹研究員 (00442731)
• Project Period (FY): 2018-04-01 – 2023-03-31
• Keywords: Sr2RuO4 / 超伝導 / 単結晶育成

Outline of Final Research Achievements

To deepen the understanding of the anisotropic superconducting state in Sr2RuO4, we initially focused on the magnetic field-temperature phase diagram. First, we succeeded in growing high-quality and large-size single crystals of Sr2RuO4 by improving the growth conditions. Next, using the grown crystals, research on this material has reached a turning point in the past quarter of a century because the superconductivity of Sr2RuO4 is found to be an even parity rather than an odd parity. Combined with research under uniaxial pressure, for instance, we found a two-component superconducting order parameter and induced magnetic order by muon spin rotation experiments. In addition, for the magnetic field-temperature phase diagram, we were able to give a strong constraint on the ``new phase'' of the field-temperature phase diagram. These results should proceed to further research on this material.

Free Research Field

固体物理

Academic Significance and Societal Importance of the Research Achievements

Sr2RuO4 は常伝導状態がフェルミ液体的挙動を示し，擬2次元的な多バンドの電子構造(フェルミ面)も詳細にわかっていることから，数ある強相関電子系物質の中でも典型的な物質の一つと考えられている．一方で，このような電子状態が舞台となって発現する超伝導については，数多くの研究がなされ四半世紀が経過するものの，まだ系統的な理解には達していないのが現状である．超伝導転移温度は1.5ケルビンと低いものの，Sr2RuO4における異方的超伝導について矛盾なく理解することは，電子間の相互作用が強いことが本質である物質系で発現する異方的超伝導の普遍的枠組み構築に向けて貢献できる．