Photoinduced Dirac-cone flattening in Ba Ni S2

Using a real-time implementation of the self-consistent G W method, we theoretically investigate the photoinduced changes in the electronic structure of the quasi-two-dimensional semimetal BaNiS2. This material features four Dirac cones in the unit cell and our simulation of the time- and momentum-resolved nonequilibrium spectral function reveals a flattening of the Dirac bands after a photodoping pulse with a 1.5 eV laser. The simulation results are consistent with the recently reported experimental data on photodoped BaNiS2 and ZrSiSe, another Dirac semimetal. A detailed analysis of the numerical data allows us to attribute the nonequilibrium modifications of the Dirac bands to (i) an increased effective temperature after the photoexcitation, which affects the screening properties of the system and (ii) to nontrivial band shifts in the photodoped state, which are mainly induced by the Fock term.