Thickness and twist angle dependent interlayer excitons in metal monochalcogenide heterostructures

• Published in: arXiv.org
• Main Authors: Zheng, Wenkai, Li, Xiang, de Quesada, Felipe, Augustin, Mathias, Lu, Zhengguang, Wilson, Matthew, Sood, Aditya, Wu, Fengcheng, Shcherbakov, Dmitry, Memaran, Shahriar, Baumbach, Ryan E, McCandless, Gregory T, Chan, Julia Y, Liu, Song, Edgar, James, Chun Ning Lau, Lui, Chun Hung, Santos, Elton, Lindenberg, Aaron, Smirnov, Dmitry, Balicas, Luis
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 15.10.2022
• Subjects: Elementary excitations; Excitons; Heterostructures; Holes (electron deficiencies); Interlayers; P-n junctions; Photoluminescence; Physics - Mesoscale and Nanoscale Physics; Separation; Stark effect; Thickness; Valence band
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2210.08296

Interlayer excitons, or bound electron-hole pairs whose constituent quasiparticles are located in distinct stacked semiconducting layers, are being intensively studied in heterobilayers of two dimensional semiconductors. They owe their existence to an intrinsic type-II band alignment between both layers that convert these into p-n junctions. Here, we unveil a pronounced interlayer exciton (IX) in heterobilayers of metal monochalcogenides, namely gamma-InSe on epsilon-GaSe, whose pronounced emission is adjustable just by varying their thicknesses given their number of layers dependent direct bandgaps. Time-dependent photoluminescense spectroscopy unveils considerably longer interlayer exciton lifetimes with respect to intralayer ones, thus confirming their nature. The linear Stark effect yields a bound electron-hole pair whose separation d is just (3.6 \pm 0.1) Å with d being very close to dSe = 3.4 Å which is the calculated interfacial Se separation. The envelope of IX is twist angle dependent and describable by superimposed emissions that are nearly equally spaced in energy, as if quantized due to localization induced by the small moiré periodicity. These heterostacks are characterized by extremely flat interfacial valence bands making them prime candidates for the observation of magnetism or other correlated electronic phases upon carrier doping.