Dynamical stability, electronic structure and optical absorption of strained penta-graphene monolayer: an ab-initio study

In this work, based on density functional theory (DFT) calculations and using more accurate many-body perturbation GW theory, we discuss how uniform biaxial strain affects the electronic structure, dynamical stability and optical absorption of the low-buckled penta-graphene (PG) monolayer. We found that under compressive strain, the PG structure becomes dynamically unstable, while under the tensile strain, it maintains the dynamical stability. Our findings reveal that PG behaves as a semiconductor with an indirect band gap of 2.27 eV at the DFT-GGA level which increases to a quasi-direct band gap of 4.62 eV in G₀W₀ approximation. However, under tensile strain, the band gap magnitude is reduced monotonically in G₀W₀ approximation. Furthermore, we employed the G₀W₀-RPA and G₀W₀-BSE approximations to compute the optical absorption spectra of the monolayer PG under compressive/tensile strain. Our results demonstrate that at the G₀W₀-BSE level, when the excitonic effects is considered, both in the strain-free and strained PG monolayer, all absorption spectra shift to lower energies (redshift). However, under tensile strain from 0 to 10%, there is an upward trend in the maximum absorption coefficient. Our results highlight the tunability of the electronic band gap and optical properties of monolayer PG under biaxial strain.