期刊
NANO LETTERS
卷 14, 期 6, 页码 3353-3357出版社
AMER CHEMICAL SOC
DOI: 10.1021/nl500823k
关键词
Graphene; twisted bilayer graphene; optical spectroscopy; GW-BSE
类别
资金
- AFOSR [FA9550-09-1-0691, FA9550-10-1-0410]
- Samsung Advanced Institute for Technology GRO Program
- Kavli Institute at Cornell for Nanoscale Science (KIC)
- Nano Material Technology Development Program through the National Research Foundation of Korea (NRF) - Ministry of Science, ICT, and Future Planning [2012M3A7B4049887]
- NSF MRSEC [DMR-1120296]
- NSF [ECS-0335765, DMR-1207141]
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [1207141] Funding Source: National Science Foundation
- National Research Foundation of Korea [2012M3A7B4049887] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
We report a systematic study of the optical conductivity of twisted bilayer graphene (tBLG) across a large energy range (1.2-5.6 eV) for various twist angles, combined with first-principles calculations. At previously unexplored high energies, our data show signatures of multiple van Hove singularities (vHSs) in the tBLG bands as well as the nonlinearity of the single layer graphene bands and their electron-hole asymmetry. Our data also suggest that excitonic effects play a vital role in the optical spectra of tBLG. Including electron-hole interactions in first-principles calculations is essential to reproduce the shape of the conductivity spectra, and we find evidence of coherent interactions between the states associated with the multiple vHSs in tBLG.
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