Interlayer Exciton Transport in MoSe₂/WSe₂ Heterostructures

Abstract

A moirésuperlattice formed by stacking two lattice mismatched transition metal dichalcogenide monolayers, functions as a diffusion barrier that affects the energy transport and dynamics of interlayer excitons (electron and hole spatially concentrated in different monolayers). In this work, we experimentally quantify the diffusion barrier experienced by interlayer excitons in hexagonal boron nitrideencapsulated molybdenum diselenide/tungsten diselenide (MoSe 2 / WSe 2 ) heterostructures with different twist angles. We observe the localization of interlayer excitons at low temperature and the temperature-activated diffusivity as a function of twist angle and hence attribute it to the deep periodic potentials arising from the moirésuperlattice. We further support the observations with theoretical calculations, Monte Carlo simulations, and a three-level model that represents the exciton dynamics at various temperatures.

Phonon scattering and exciton localization: molding exciton flux in two dimensional disorder energy landscape

“…The successful encapsulation with hBN can effectively suppress the disorder including local fluctuations of inherent material properties (such as chemical and structural composition, doping or strain) and external dielectric environment. Therefore, exciton diffusion experiments on hBN encapsulated 2D semiconductor were performed [44,52,69,70], and the crucial role of disorder in exciton diffusion was verified. Naturally, we can expect a greater optimal diffusion coefficient in the hBN encapsulated 2D semiconductor at lower temperatures that exciton-phonon scattering is mitigated simultaneously.…”

Self-trapped interlayer excitons in van der Waals heterostructures

“…dergoing a transition from negative to positive (∆E b = ∆E s -∆E c ). This allows the STS to be divided into two types: type I with the energy shifting downwards from the free exciton state (FE) and type II with the energy shifting upwards, as illustrated in Figure 1 (b), indicating that it is insufficient to judge the STS only by the increasing of binding energy in most experiments [34,[61][62][63][64]. Except the internal distance h 0 , the spatial distance D between electron and hole has a direct impact on binding energy since it determines the Coulomb interaction of electron-hole pair and thus the variation of ∆E b , as shown in Figure 1 (d).…”

Dipole moment and pressure dependent interlayer excitons in MoSSe/WSSe heterostructures

“…[32][33][34] There are also a multitude of attempts to control qualitatively the band structures and electronic wave function through twisting the monolayer to produce a periodic moiré potential and moiré excitons. 8,29,35,36 Furthermore, the method of alloying monolayers to generate a class of WS 2(1−x) Se 2x materials has also been developed to continuously adjust the band gap to improve the light-matter interaction controlled by excitons. 37,38 The idea of applying the Janus concept to TMDCs by YC Cheng et al has recently been successfully realized experimentally, and as a result a new type of monolayer material MXY (M = Mo and W and X, Y = S and Se) has been synthesized.…”