Exciton in phosphorene: Strain, impurity, thickness, and heterostructure

Abstract

Reduced electron screening in two-dimension plays a fundamental role in determining exciton properties, which dictates optoelectronic and photonic device performances. Considering the explicit electron-hole interaction within the GW −Bethe-Salpeter formalism, we first study the excitonic properties of pristine phosphorene and investigate the effects of strain and impurity coverage. The calculations reveal strongly bound exciton in these systems with anisotropic spatial delocalization. Further, we present a simplified hydrogenic model with anisotropic exciton mass and effective electron screening as parameters, and the corresponding results are in excellent agreement with the present GW −BSE calculations. The simplified model is then used to investigate exciton renormalization in few-layer and heterostructure phosphorene. The changes in carrier effective mass along with increasing electron screening renormalizes the exciton binding in these systems. We establish that the present model, where the parameters are calculated within computationally less expensive first-principles calculations, can predict exciton properties with excellent accuracy for larger two-dimensional systems, where the many-body GW −BSE calculations are impossible. arXiv:1810.11994v1 [cond-mat.mes-hall]

Layer‐Dependent Electronic and Optical Properties of 2D Black Phosphorus: Fundamentals and Engineering

“…[176] Several groups calculated that the exciton binding energy in freestanding monolayer BP is as large as ≈800 meV. [58,59,72,[177][178][179] Rodin et al shows that E b decreases as the substrate dielectric constant increases. For instance, in free-standing monolayer BP, E b is calculated to be 760 meV, with SiO 2 supporting, it sharply reduces to ≈400 meV.…”

“…[ 176 ] Several groups calculated that the exciton binding energy in free‐standing monolayer BP is as large as ≈800 meV. [ 58,59,72,177–179 ] Rodin et al. shows that E b decreases as the substrate dielectric constant increases.…”

“…[ 177 ] Moreover, it is also theoretically found that E b is strongly layer‐dependent in 2D BP. [ 58,59,178 ]…”

van der Waals heterostructure for photocatalysis: Graphitic carbon nitride and Janus transition-metal dichalcogenides

“…Previously, we have used a similar approach to describe exciton binding in anisotropic phosphorene derivatives, which also correctly described the exciton renormalization in the few-layer phosphorene and heterostructures. [9] To establish the applicability of the hydrogenic model of exciton for the composite systems, we first calculated the exciton binding for the single-layer MoXY by considering the explicit electron-hole interaction within the many-body perturbation-theory-based GW method plus Bethe-Salpeter equation (BSE) formalism, [56][57][58][59] and compare the results with the model calculations. Model calculations of 0.58 and 0.57 eV exciton binding for the Janus MoSSe and MoSTe are in excellent (Table II), which is favourable for photocatalysis.…”

Excitons in Two-Dimensional Materials

“…2D materials possess excellent mechanical flexibility, making them stable under high compressive, tensile, and bending strain [97]. Applying mechanical strain on 2D materials, their bandgaps will reduce, increase, or transit from direct to indirect, thus resulting in a strain-dependent exciton binding energy [98][99][100][101][102][103]. Based on density functional theory, Su et al investigated the natural physical properties of TMD monolayers and hBN-TMD heterostructures, finding that they have distinctive bandgap and exciton binding energy under compressive strain ( Figure 11a) [98].…”