Miroslav Kolos and František Karlický in cooperation with colleagues from India published a new paper!

Phonon Assisted Exciton Processes in Two-Dimensional Tungsten Monocarbide

Link here: https://doi.org/10.1021/acs.jpcc.4c02062

Abstract:

In this study, we utilized a rigorous ab initio-based finite momentum Bethe–Salpeter equation to investigate the photoluminescence emission in two-dimensional hexagonal tungsten carbide (h-WC). This thermodynamically stable monolayer exhibits an indirect optical gap, resulting in phonon-assisted emission. We observe that light absorption is a direct process centered around the direct quasiparticle gap, while light emission is indirect and requires modes between Γ–M in the phonon dispersion. The emission lines feature prominent phonon replicas at cryogenic temperatures, particularly near-infrared wavelengths (1.09 and 1.17 eV), and we observe exciton thermalization with the crystal beyond 25 K. Additionally, nonradiative recombination is a remarkably fast process, on the order of a few femtoseconds (4.8 fs at 0 K and 2.8 fs at 300 K), compared to radiative recombination (2.3 ps at 0 K and 214 ns at 300 K). These optical characteristics of 2D h-WC may facilitate the promise of photon-emitter devices for near-infrared signal communication.