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arXiv · 1608.05586

Ultrafast Electronic Band Gap Control in an Excitonic Insulator

Selene Mor·Marc Herzog·Denis Golež·Philipp Werner·Martin Eckstein·Naoyuki Katayama·Minoru Nohara·Hide Takagi·Takashi Mizokawa·Claude Monney·Julia Stähler
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Abstract

We report on the nonequilibrium dynamics of the electronic structure of the layered semiconductor Ta$_2$NiSe$_5$ 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 $F_{C}$. Hartree-Fock calculations reveal that this effect can be explained by the presence of the low-temperature excitonic insulator phase of Ta$_2$NiSe$_5$, whose order parameter is connected to the gap size. This work demonstrates the ability to manipulate the band gap of Ta$_2$NiSe$_5$ with light on the femtosecond time scale.

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Selene Mor, Marc Herzog, Denis Golež, Philipp Werner, Martin Eckstein, Naoyuki Katayama, Minoru Nohara, Hide Takagi, Takashi Mizokawa, Claude Monney, Julia Stähler. 2016-08-19. Ultrafast Electronic Band Gap Control in an Excitonic Insulator. https://doi.org/10.1103/physrevlett.119.086401

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