Thickness- and Twist-Angle-Dependent Interlayer Excitons in Metal Monochalcogenide Heterostructures

Wenkai Zheng, Li Xiang, Felipe A. De Quesada, Mathias Augustin, Zhengguang Lu, Matthew Wilson, Aditya Sood, Fengcheng Wu, Dmitry Shcherbakov, Shahriar Memaran, Ryan E. Baumbach, Gregory T. McCandless, Julia Y. Chan, Song Liu, James H. Edgar, Chun Ning Lau, Chun Hung Lui, Elton J.G. Santos, Aaron Lindenberg, Dmitry SmirnovLuis Balicas

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

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, γ-InSe on ϵ-GaSe, whose pronounced emission is adjustable just by varying their thicknesses given their number of layers dependent direct band gaps. 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 ± 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.

Original languageEnglish (US)
Pages (from-to)18695-18707
Number of pages13
JournalACS Nano
Volume16
Issue number11
DOIs
StatePublished - Nov 22 2022
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General Engineering
  • General Materials Science
  • General Physics and Astronomy

Keywords

  • Stark effect
  • heterostructures
  • interlayer excitons
  • metal monochalcogenides
  • moiré potential
  • photoluminescence

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