2019 Fiscal Year Final Research Report
Elucidation of mechanism of superconductivity in multiband superconductors by ultrasonic measurements under hydrostatic pressures
| Project/Area Number |
17K05538
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Condensed matter physics II
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| Research Institution | Niigata University |
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Principal Investigator |
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| Project Period (FY) |
2017-04-01 – 2020-03-31
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| Keywords | マルチバンド超伝導 / 超音波計測 / 静水圧 / 電気四極子 / 弾性定数 / 超音波吸収係数 / 鉄系超伝導体 / 励起子絶縁体 |
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| Outline of Final Research Achievements |
In order to elucidate mechanism of superconductivity in multi-band iron-based superconductors Ba(Fe1-xCox)2As2, we have performed ultrasonic measurements under high magnetic fields and hydrostatic pressures. The huge softening of the elastic constant C66 in Ba(Fe1-xCox)2As2 shows very small field dependence under high magnetic fields. The sample of concentration near the quantum critical point has the quadrupole-strain interaction, which is larger than the other concentrations. In addition, the C66 of this sample shows large pressure dependence. Theses results suggest that the quadrupole fluctuation, which are the origin of the huge softening of C66, also plays an important role in the mechanism of superconductivity.
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| Free Research Field |
物性物理学
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| Academic Significance and Societal Importance of the Research Achievements |
縮退したマルチバンド構造を持つ鉄系超伝導体Ba(Fe1-xCox)2As2は、弾性定数C66が強磁場下でも磁場依存性が小さいことや、構造相転移の量子臨界点近傍では四極子－歪み相互作用が大きいこと、またC66の静水圧力依存性が大きいことが世界で初めて明らかになった。これは、以前、我々が提案した四極子がもたらす十六極子の揺らぎが超伝導のドライブフォースの1つであることを強く支持している。これは、最近精力的に研究が行われている圧力下で構造相転移の量子臨界点近傍で超伝導を示す励起子絶縁体候補物質などでも同様の議論をできる可能性があり、新しい発現機構を持つ超伝導の物理の発展に強く寄与すると考えられる。
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