@article{MorHerzogGolezetal.2017, author = {Mor, Selene and Herzog, Marc and Golez, Denis and Werner, Philipp and Eckstein, Martin and Katayama, Naoyuki and Nohara, Minoru and Takagi, Hide and Mizokawa, Takashi and Monney, Claude and Staehler, Julia}, title = {Ultrafast Electronic Band Gap Control in an Excitonic Insulator}, series = {Physical review letters}, volume = {119}, journal = {Physical review letters}, publisher = {American Physical Society}, address = {College Park}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.119.086401}, pages = {11559 -- 11567}, year = {2017}, abstract = {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 F-C = 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.}, language = {en} }