Abstract
Recently, monolayer group–VIB transition metal dichalcogenides (TMDs) serves as a promising platform for two dimensional (2D) material physics, not only because of their direct bandgap energy structure, but also due to the optical excitonic valley polarization. Furthermore, the bright exciton has two valley pseudospin configurations characterized by valley index +K and -K.
In the excitonic valley pseudospin configurations, the Coulomb exchange interaction of electron-hole pair causes a considerable valley-orbit coupling, which breaks degenerate of pseudospin level. Each pseudospin branch shows the behavior of the Dirac particle with chirality index I = 2. The property of excitonic transport perhaps emerges novel phenomenon than typical semiconducting 2D zero-bandgap material. In this topic, we have calculated the transmission and reflection probability of excitonic quasiparticle through a valley-orbital coupling strength modulation model in 2D TMDs material. In step-function case, the lower branch incident quasiparticle is nearly transparency, while the intra-branch transmission and reflection probability obey the Snell-Descartes law of optics when upper branch incidences.
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