Aurelie Champagne1,2,Jonah Haber2,Supavit Pokawanvit3,Souvik Biswas4,Diana Qiu5,Harry Atwater4,Felipe da Jornada3,Jeffrey Neaton2,1,6
Lawrence Berkeley National Laboratory1,University of California, Berkeley2,Stanford University3,California Institute of Technology4,Yale University5,Kavli Energy NanoScience Institute6
Aurelie Champagne1,2,Jonah Haber2,Supavit Pokawanvit3,Souvik Biswas4,Diana Qiu5,Harry Atwater4,Felipe da Jornada3,Jeffrey Neaton2,1,6
Lawrence Berkeley National Laboratory1,University of California, Berkeley2,Stanford University3,California Institute of Technology4,Yale University5,Kavli Energy NanoScience Institute6
Quantum confinement and reduced dielectric screening in two-dimensional (2D) materials can result in enhanced many-body Coulomb interactions which in turn lead to large exciton binding energies of the order of several hundreds meV. A modification in the dielectric environment of 2D systems, such as the presence of charged free carriers, can screen the many-body interactions and modify the quasiparticle (QP) band gap as well as the excited state properties (energies and oscillator strengths). In general, the optical properties of bulk systems including electron-hole interactions are computed with ab initio many-body perturbation theory, using the GW plus Bethe-Salpeter equation (BSE) approach using the static random phase approximation. However, the static approximation is valid only if the exciton binding energy is negligible in comparison to the plasmon energy, which is no longer the case in 2D materials such as transition metal dichalcogenides (TMDs), and even less true for the carrier plasmon energy which is of the same order as the exciton binding energy. Here, we perform ab initio GW+BSE calculations on a MoTe<sub>2</sub> monolayer. We introduce a modified plasmon pole model (PPM) that explicitly accounts for both dynamical excitonic effects and local field effects, to accurately capture QP band gap renormalization, as well as modifications of the excitonic and optical properties, in doped MoTe<sub>2</sub> monolayers. Using this model, we find that, in agreement with photoluminescence measurements, neutral excitation energies remain almost unchanged upon doping, a consequence of a similar reduction in both the QP band gap energy and exciton binding energies. Both the dynamical screening and local field effects captured by our PPM lead to good quantitative agreement with experiments and enable studies of more complex charged excitations, e.g., trions, in these and other doped 2D systems.<br/><br/>This work is supported by the Center for Computational Study of Excited-state Phenomena in Energy Materials (C2SEPEM), funded by the US Department of Energy (DOE) under contract No. DE-AC02-05CH11231. Computational resources are provided by the National Energy Research Scientific Computing Center (NERSC), under contract No. DE-AC02-05CH11231. AC acknowledges the support from Wallonie Bruxelles International (WBI).