Double\nIndirect Interlayer Exciton in a MoSe₂/WSe₂ van\nder Waals Heterostructure

Abstract

An emerging class\nof semiconductor heterostructures involves stacking\ndiscrete monolayers such as transition metal dichalcogenides (TMDs)\nto form van der Waals heterostructures. In these structures, it is\npossible to create interlayer excitons (ILEs), spatially indirect,\nbound electron–hole pairs with the electron in one TMD layer\nand the hole in an adjacent layer. We are able to clearly resolve\ntwo distinct emission peaks separated by 24 meV from an ILE in a MoSe₂/WSe₂ heterostructure fabricated using state-of-the-art\npreparation techniques. These peaks have nearly equal intensity, indicating\nthey are of common character, and have <i>opposite</i> circular\npolarizations when excited with circularly polarized light. <i>Ab initio</i> calculations successfully account for these observations:\nthey show that both emission features originate from excitonic transitions\nthat are indirect in momentum space and are split by spin–orbit\ncoupling. Also, the electron is strongly hybridized between both the\nMoSe₂ and WSe₂ layers, with significant weight\nin both layers, contrary to the commonly assumed model. Thus, the\ntransitions are not purely interlayer in character. This work represents\na significant advance in our understanding of the static and dynamic\nproperties of TMD heterostructures.