Observation of soft Leggett mode in superconducting CaKFe4As4

We study the ultrafast dynamics of the multiband iron-based superconductor CaKFe4As4 via time-resolved optical reflectivity. We observe a long-lived 5- GHz oscillation of the reflection changes within the superconducting regime. We assign this low-frequency oscillation to a soft Leggett mode associa...

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Veröffentlicht in:	Physical review. B 2020-10, Vol.102 (14)
Hauptverfasser:	Zhao, S Z, Song, Hai-Ying, Hu, L Hu, Xie, T, Liu, C, Luo, H Q, Jiang, Cong-Ying, Zhang, Xiu, Nie, X C, Meng, Jian-Qiao, Duan, Yu-Xia, Liu, Shi-Bing, Xie, Hong-Yi, Liu, H Y
Format:	Artikel
Sprache:	eng
Schlagworte:	Broken symmetry Superconductivity
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Zusammenfassung:	We study the ultrafast dynamics of the multiband iron-based superconductor CaKFe4As4 via time-resolved optical reflectivity. We observe a long-lived 5- GHz oscillation of the reflection changes within the superconducting regime. We assign this low-frequency oscillation to a soft Leggett mode associated with the collective fluctuation of multiple phase differences between Cooper pair condensates. Our observation evidences the presence of the time-reversal-symmetry breaking state in superconducting CaKFe4As4.
ISSN:	2469-9950 2469-9969
DOI:	10.1103/PhysRevB.102.144519