Stacking angle-tunable photoluminescence from interlayer exciton states in twisted bilayer graphene
| Autor: | Lujie Huang, Hiral Patel, Cheol-Joo Kim, Matt W. Graham, Jiwoong Park |
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| Rok vydání: | 2019 |
| Předmět: |
0301 basic medicine
Photoluminescence Materials science Absorption spectroscopy Science Exciton Van Hove singularity Stacking Physics::Optics General Physics and Astronomy 02 engineering and technology Molecular physics Article General Biochemistry Genetics and Molecular Biology law.invention Condensed Matter::Materials Science 03 medical and health sciences law Photoluminescence excitation lcsh:Science Multidisciplinary Condensed Matter::Other Graphene General Chemistry Condensed Matter::Mesoscopic Systems and Quantum Hall Effect 021001 nanoscience & nanotechnology 030104 developmental biology lcsh:Q 0210 nano-technology Bilayer graphene |
| Zdroj: | Nature Communications, Vol 10, Iss 1, Pp 1-7 (2019) Nature Communications |
| ISSN: | 2041-1723 |
| Popis: | Twisted bilayer graphene (tBLG) is a metallic material with two degenerate van Hove singularity transitions that can rehybridize to form interlayer exciton states. Here we report photoluminescence (PL) emission from tBLG after resonant 2-photon excitation, which tunes with the interlayer stacking angle, θ. We spatially image individual tBLG domains at room-temperature and show a five-fold resonant PL-enhancement over the background hot-electron emission. Prior theory predicts that interlayer orbitals mix to create 2-photon-accessible strongly-bound (~0.7 eV) exciton and continuum-edge states, which we observe as two spectral peaks in both PL excitation and excited-state absorption spectra. This peak splitting provides independent estimates of the exciton binding energy which scales from 0.5–0.7 eV with θ = 7.5° to 16.5°. A predicted vanishing exciton-continuum coupling strength helps explain both the weak resonant PL and the slower 1 ps−1 exciton relaxation rate observed. This hybrid metal-exciton behavior electron thermalization and PL emission are tunable with stacking angle for potential enhancements in optoelectronic and fast-photosensing graphene-based applications. Interlayer electronic states in twisted bilayer graphene are characterized by flat-band regions hosting many-body electronic effects. Here, the authors observe two-photon photoluminescence excitation and excited-state absorption spectra on graphene containing a variety of twist angles to access the dark exciton transitions and estimate the exciton binding energy. |
| Databáze: | OpenAIRE |
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