Enhanced third-harmonic generation by manipulating the twist angle of bilayer graphene

Seongju Ha, Nam Hun Park, Hyeonkyeong Kim, Jiseon Shin, Jungseok Choi, Sungmin Park, Ji Yun Moon, Kwanbyung Chae, Jeil Jung, Jae Hyun Lee, Youngdong Yoo, Ji Yong Park, Kwang Jun Ahn, Dong Il Yeom

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

Twisted bilayer graphene (tBLG) has received substantial attention in various research fields due to its unconventional physical properties originating from Moiré superlattices. The electronic band structure in tBLG modified by interlayer interactions enables the emergence of low-energy van Hove singularities in the density of states, allowing the observation of intriguing features such as increased optical conductivity and photocurrent at visible or near-infrared wavelengths. Here, we show that the third-order optical nonlinearity can be considerably modified depending on the stacking angle in tBLG. The third-harmonic generation (THG) efficiency is found to significantly increase when the energy gap at the van Hove singularity matches the three-photon resonance of incident light. Further study on electrically tuneable optical nonlinearity reveals that the gate-controlled THG enhancement varies with the twist angle in tBLG, resulting in a THG enhanced up to 60 times compared to neutral monolayer graphene. Our results prove that the twist angle opens up a new way to control and increase the optical nonlinearity of tBLG, suggesting rotation-induced tuneable nonlinear optics in stacked two-dimensional material systems.

Original languageEnglish
Article number19
JournalLight: Science and Applications
Volume10
Issue number1
DOIs
StatePublished - Dec 2021

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