FeSexTe1−x compounds present a complex phase diagram, ranging from the nematicity of FeSe to the (π,π) magnetism of FeTe. We focus on FeSe0.4Te0.6, where the nematic ordering is absent at equilibrium. We use a time-resolved approach based on femtosecond light pulses to study the dynamics following photoexcitation in this system. The use of polarization-dependent time- and angle-resolved photoelectron spectroscopy allows us to reveal a photoinduced nematic metastable state, whose stabilization cannot be interpreted in terms of an effective photodoping. We argue that the 1.55 eV photon-energy-pump-pulse perturbs the C4 symmetry of the system triggering the realization of the nematic state. The possibility to induce nematicity using an ultra-short pulse sheds a new light on the driving force behind the nematic symmetry breaking in iron-based superconductors. Our results weaken the idea that a low-energy coupling with fluctuations is a necessary condition to stabilize the nematic order and ascribe the origin of the nematic order in iron-based superconductors to a clear tendency of those systems towards orbital differentiation due to strong electronic correlations induced by the Hund's coupling.
@article{arxiv.1905.12448,
title = {Photoinduced nematic state in FeSe$_{0.4}$Te$_{0.6}$},
author = {Laura Fanfarillo and Damir Kopić and Andrea Sterzi and Giulia Manzoni and Alberto Crepaldi and Vladimir Tsurkan and Dorina Croitori and Joachim Deisenhofer and Fulvio Parmigiani and Massimo Capone and Federico Cilento},
journal= {arXiv preprint arXiv:1905.12448},
year = {2021}
}