Quasiparticle, exciton, and optical properties in violet and blue phosphorenes

Strong many-body effects arising from enhanced electron-electron and electron-hole interactions will give rise to novel phenomena in two-dimensional (2D) materials. Accurate computational method like ab initio many-body perturbation theory is necessary to calculate the quasiparticle and optical properties in 2D materials [1]. In this talk, we will discuss our G0W0-BSE calculations on violet (Hittorf's) and blue phosphorenes, two new 2D candidates in the phosphorus allotropes family. We first demonstrate a direct-wide-band-gap semiconductor with anisotropic electron-hole excitation of Hittorf's phosphorene monolayer [2]. In addition, the relatively large thickness makes it possible to modulate the band gap and optical properties substantially via a vertical electric field and this strong quantum-confined Stark effect shows its potential in 2D optoelectronics devices [3]. For blue phosphorene, we reveal the unusual strain dependence of quasiparticle, optical, and exciton properties, where the funnel effect could be realized to overcome its indirect-band-gap nature for the green or blue light-emitting applications [4]. We also show the stronger exciton effect in few-layer blue phosphorene [5]. Compared to other 2D materials [6], it was revealed that the parallel band structure in these indirect band gap semiconductors plays a crucial role.