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Free keywords:
Electronic structure, Infrared devices, Infrared lasers, Iron-based Superconductors, Laser excitation, Phonons, Photoelectron spectroscopy, Ultrafast lasers, Ultraviolet lasers, Coherent excitations, Equilibrium state, Experimental evidence, Extreme Ultraviolet, Meta-stable state, Near-infrared lasers, Photoexcited carriers, Ultrafast excitation, Excited states
Abstract:
Changes of the electronic structure of FeTe1−xSex (x = 0, 0.3) upon ultrafast excitation with near-infrared laser pulses are investigated using time- and angle-resolved extreme ultraviolet photoemission spectroscopy. At different temperatures and for different doping levels we observe a global oscillation of energy bands near the Fermi energy driven by the coherent excitation of the A1g(Te) phonon mode in FeTe1−xSex. Prominently, photo-induced band shifts and a spectral weight reduction persist for at least 300 ps, long after the decay of the photo-excited carriers and the damping of the coherent phonons. We argue that the system escapes from the original equilibrium state and is transiently trapped in a possibly metastable state envisioning a purely optical means of manipulating the electronic structure in an iron-based superconductor. © 2021 Elsevier B.V.