Femtosecond electron-phonon lock-in by photoemission and x-ray free-electron laser

The interactions that lead to the emergence of superconductivity in iron-based materials remain a subject of debate. It has been suggested that electron-electron correlations enhance electron-phonon coupling in iron selenide (FeSe) and related pnictides, but direct experimental verification has been...

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Vydáno v:Science (American Association for the Advancement of Science) Ročník 357; číslo 6346; s. 71
Hlavní autoři: Gerber, S, Yang, S-L, Zhu, D, Soifer, H, Sobota, J A, Rebec, S, Lee, J J, Jia, T, Moritz, B, Jia, C, Gauthier, A, Li, Y, Leuenberger, D, Zhang, Y, Chaix, L, Li, W, Jang, H, Lee, J-S, Yi, M, Dakovski, G L, Song, S, Glownia, J M, Nelson, S, Kim, K W, Chuang, Y-D, Hussain, Z, Moore, R G, Devereaux, T P, Lee, W-S, Kirchmann, P S, Shen, Z-X
Médium: Journal Article
Jazyk:angličtina
Vydáno: United States 07.07.2017
ISSN:1095-9203, 1095-9203
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Popis
Shrnutí:The interactions that lead to the emergence of superconductivity in iron-based materials remain a subject of debate. It has been suggested that electron-electron correlations enhance electron-phonon coupling in iron selenide (FeSe) and related pnictides, but direct experimental verification has been lacking. Here we show that the electron-phonon coupling strength in FeSe can be quantified by combining two time-domain experiments into a "coherent lock-in" measurement in the terahertz regime. X-ray diffraction tracks the light-induced femtosecond coherent lattice motion at a single phonon frequency, and photoemission monitors the subsequent coherent changes in the electronic band structure. Comparison with theory reveals a strong enhancement of the coupling strength in FeSe owing to correlation effects. Given that the electron-phonon coupling affects superconductivity exponentially, this enhancement highlights the importance of the cooperative interplay between electron-electron and electron-phonon interactions.
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ISSN:1095-9203
1095-9203
DOI:10.1126/science.aak9946