Mor, Selene Herzog, Marc Golež, Denis Werner, Philipp Eckstein, Martin Katayama, Naoyuki Nohara, Minoru Takagi, Hide Mizokawa, Takashi Monney, Claude Stähler, Julia 2017-08-23 We report on the nonequilibrium dynamics of the electronic structure of the layered semiconductor Ta2NiSe5 investigated by time- and angle-resolved photoelectron spectroscopy. We show that below the critical excitation density of FC=0.2 mJ cm−2, the band gap narrows transiently, while it is enhanced above FC. Hartree-Fock calculations reveal that this effect can be explained by the presence of the low- temperature excitonic insulator phase of Ta2NiSe5, whose order parameter is connected to the gap size. This work demonstrates the ability to manipulate the band gap of Ta2NiSe5 with light on the femtosecond time scale. application/pdf https://folia.unifr.ch/global/documents/306110 https://folia.unifr.ch/documents/306110/files/wer_ueb.pdf eng info:eu-repo/semantics/altIdentifier/doi/10.1103/PhysRevLett.119.086401 info:eu-repo/semantics/openAccess License undefined Physical Review Letters. - 2017, vol. 119, no. 8, p. 086401 info:eu-repo/classification/udc/53 Ultrafast electronic band gap control in an excitonic insulator http://purl.org/coar/resource_type/c_6501