Excitons and trions with negative effective masses in two-dimensional semiconductors

Abstract

AbstractWe study theoretically fundamental Coulomb-correlated complexes: neutral and charged excitons, also known as trions, in transition metal dichalcogenides monolayers. We focus on the situation where one of the electrons occupies an excited, high-lying, conduction band characterized by a negative effective mass. We develop the theory of such high-lying excitons and trions with negative effective mass and demonstrate the key role of the non-parabolicity of the high-lying conduction band dispersion in the formation of the bound exciton and trion states. We present simple, accurate and physically justified trial wavefunctions for calculating the binding energies of Coulomb-bound complexes and compare the results of variational calculations with those of a fully numerical approach. Within the developed model, we discuss recent experimental results on the observation of high-lying negative effective mass trions.