Anisotropic exciton excitations and optical properties of Hittorf's phosphorene

Due to the exciton effects, two-dimensional materials have displayed strong light-matter interactions. Here, by considering many-body effects of electron-electron and electron-hole interactions, we provide a more accurate quasiparticle electronic structure, exciton, and optical absorption spectrum of Hittorf's phosphorene, a monolayer of Hittorf's (or violet) phosphorus obtained recently via exfoliation method. The fibrous nature of the crystal structure with twofold rotation symmetry leads to anisotropic electron-hole excitations, and an obvious dichroism in optical absorption is revealed over a wide spectral range. The first exciton state located at 2.4 eV is bright with a large binding energy of 0.9 eV and a lifetime of 18 ns. These unusual excitonic and optical properties demonstrate its potential applications in optoelectronics.