Theory of edge-state optical absorption in two-dimensional transition metal dichalcogenide flakes

Trushin, M and Kelleher, EJR and Hasan, T (2016) Theory of edge-state optical absorption in two-dimensional transition metal dichalcogenide flakes. Physical Review B, 94. ISSN 2469-9950

Abstract

We develop an analytical model to describe sub-band-gap optical absorption in two-dimensional semiconducting transition metal dichalcogenide (s-TMD) nanoflakes. The material system represents an array of few-layer molybdenum disulfide crystals, randomly orientated in a polymer matrix. We propose that optical absorption involves direct transitions between electronic edge states and bulk bands, depends strongly on the carrier population, and is saturable with sufficient fluence. For excitation energies above half the band gap, the excess energy is absorbed by the edge-state electrons, elevating their effective temperature. Our analytical expressions for the linear and nonlinear absorption could prove useful tools in the design of practical photonic devices based on s-TMDs.