2020 Fiscal Year Final Research Report
Symmetry breaking phenomena in the pseudogap state of cuprates
| Project/Area Number |
18H01177
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Review Section |
Basic Section 13030:Magnetism, superconductivity and strongly correlated systems-related
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| Research Institution | Kyoto University |
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Principal Investigator |
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| Project Period (FY) |
2018-04-01 – 2021-03-31
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| Keywords | 銅酸化物高温超伝導体 / 擬ギャップ相 / 回転対称性の破れ / 電子ネマティック秩序 / イリジウム酸化物 / アナポール秩序 / 奇パリティ秩序 / 磁気トルク測定 |
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| Outline of Final Research Achievements |
Elucidating the nature of the pseudogap state that emerges in a wide range of the phase diagram of cuprate superconductors is one of the most enigmatic issues in modern condensed matter physics. Here, by using ultra-sensitive magnetic torque experiments, we investigate the pseudogap state of a tetragonal cuprate superconductor HgBa2CuO4+d (Hg1201) with only one CuO2 layer per primitive cell. Our key findings are two-folded: First, we found a distinct two-fold in-plane anisotropy that sets in below the pseudogap temperature T*, providing thermodynamic evidence for an electronic nematic transition. Second, we found that the nematic director in Hg1201 orients along the diagonal direction in the CuO2 square lattice, in sharp contrast to the bond nematicity along the Cu-O-Cu direction. These results highlight that the pseudogap state is a distinct ordered phase, that is different from charge-density-wave or its precursors along the Cu-O-Cu bond direction.
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| Free Research Field |
凝縮系物理学実験
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| Academic Significance and Societal Importance of the Research Achievements |
本研究成果は、擬ギャップ相での回転対称性の破れが系に依存することを示しており、現代物理学における最重要問題の一つとされる擬ギャップ状態の微視的起源を明らかにする上で極めて重要な結果と考えられる。さらに、本研究では新しい系として、5dイリジウム酸化物Sr2IrO4の隠れた秩序状態について、これが奇パリティのアナポール秩序であることを示した。これらはモット絶縁近傍において強く相互作用する電子系が示す新奇電子状態の存在を示したものであり、学術的に意義のあるものといえる。
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