Photo-induced Dirac cone flattening in BaNiS$_2$

TL;DR

This study uses advanced theoretical simulations to show how photo-excitation causes Dirac bands in BaNiS$_2$ to flatten, aligning with experimental observations and revealing the underlying electronic mechanisms involved.

Contribution

The paper introduces a real-time self-consistent $GW$ approach to analyze photo-induced electronic structure changes in BaNiS$_2$, highlighting band flattening and its causes.

Findings

Dirac bands flatten after photo-doping with 1.5 eV laser

Simulation aligns with experimental data on BaNiS$_2$ and ZrSiSe

Band modifications are due to increased effective temperature and Fock term effects

Abstract

Using a real-time implementation of the self-consistent $GW$ method, we theoretically investigate the photo-induced changes in the electronic structure of the quasi two-dimensional semi-metal BaNiS$_2$. 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 photo-doping pulse with a 1.5 eV laser. The simulation results are consistent with the recently reported experimental data on photo-doped BaNiS$_2$ and ZrSiSe, another Dirac semi-metal. 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 photo-excitation, which affects the screening properties of the system, and (ii) to nontrivial band shifts in the photo-doped state, which are mainly induced by the Fock term.