Atomically Thin van der Waals Semiconductors—A Theoretical Perspective

Abstract

2D semiconductors and their heterostructures have developed into a flourishing research field. A more or less simultaneous start of experimental and theoretical developments has led to continuous advancements in both branches of physics that continue to benefit from one another in an exemplary manner. This article gives an overview of the theoretical advancements that have resulted from a decade of research on 2D van der Waals materials and reviews current theoretical methods, focussing on exciton-plasma balance, excited-state optics, and laser physics.

Excitonic theory of doping-dependent optical response in atomically thin semiconductors

“…Filling factors (1-f ζ e/h,k ) contributing to Eq. ( 22) were neglected due to a systematic truncation to linear doping densities valid for doping densities Ne/h and trion Bohr radii a t satisfying N e/h (a t ) 2 1 [29]. This condition is fulfilled in the range of low doping densities, where filling factors in Eq.…”

“…Atomically thin semiconductors combine almost twodimensional confinement of carriers with weak dielectric screening from the environment which leads to strong Coulomb interaction energies compared to the thermal energies [1,2]. The strong Coulomb attraction between electrons in the conduction bands and holes in the valence bands induces bound electron-hole pairs, called excitons, with binding energies of several hundred meV in monolayer transition metal dichalcogenides (TMDCs) [3][4][5][6][7][8][9].…”

Optical amplification in a CDW-phase of a quasi-two dimensional material

“…Recently, there has been a lot of interest in novel optoelectronic materials and photonic devices and also progresses on TMDC lasers are reported. The discussion focuses mainly on materials like M oT e 2 , M oS 2 , M oSe 2 , W S 2 , W Se 2 , W T e 2 with band gaps in the eV regime, [80][81][82][83][84][85][86][87][88][89] because those materials are the most promising candidates for photonic devices. They possess large exciton binding energies and the maximum achievable gain of those materials exceeds ordinary semiconductor materials like GaAs.…”

Impact of optically pumped non-equilibrium steady states on luminescence emission of atomically-thin semiconductor excitons

“…Introduction: Tightly bound excitons and strong exciton interactions in transition metal dichalcogenides have stimulated research over the last years [1][2][3][4] . Optically addressable excitons are located at the non-equivalent K/K valleys in the hexagonal Brillouin zone, which can be addressed with light of opposite circular polarization.…”