2D materials: a new playground for nonlinear optics

摘要：Atomically thin two dimensional materials have recently spurred a great of interests due to their unique mechanic, electronic, optical and magnetic properties. And often these properties could be greatly tuned by external stimuli such as electric, magnetic and force fields. Individual member in this class of 2D materials is characteristic in term of structural symmetry. Moreover, the structural symmetry could also be tuned, depending on how monolayers are stacked on one another. These variations in symmetry have given rise to even richer properties among different 2D materials and their homo-/hetero-structures. Therefore, they provide a new playground for nonlinear optics because of its sensitivity to symmetry. Vice versa, nonlinear optics becomes a powerful technique to study 2D materials. In this talk, I will present some of our recent results on nonlinear optical microscopy and spectroscopy of 2D materials, including graphene[1-2], transition metal dichalcogenides[3-5] and chromium trihalides[6].[1] Valley and band structure engineering of folded MoS2 bilayers.T. Jiang, H.R. Liu, D. Huang, S. Zhang, Y.G. Li, X.G. Gong*, Y.R. Shen, W.T. Liu*, S.W. Wu*, Nature Nanotechnology 9, 825-829 (2014).[2] Kinetic Nature of Grain Boundary Formation in As-grown MoS2 Monolayers.J.X. Cheng#, T. Jiang#, Q.Q. Ji, Y. Zhang, Z.M. Li, Y.W. Shan, Y.F. Zhang, X.G. Gong, W.T. Liu, S.W. Wu*, Advanced Materials 27, 4069-4074 (2015).[3] Gate-tunable third-order nonlinear optical response of massless Dirac fermions in graphene.Tao Jiang#, Di Huang#, Jinluo Cheng, Xiaodong Fan, Zhihong Zhang, Yuwei Shan, Yangfan Yi, Yunyun Dai, Lei Shi, Kaihui Liu, Changgan Zeng, Jian Zi, J.E. Sipe, Yuen-Ron Shen, Wei-Tao Liu*, Shiwei Wu*, Nature Photonics 12, 430-436 (2018). [4] Stacking-symmetry governed second harmonic generation in graphene trilayers., Yuwei Shan, Yingguo Li, Di Huang, Qingjun Tong, Wang Yao, Wei-Tao Liu, Shiwei Wu*, Science Advances 4, eaat0074 (2018)[5] Doping-induced second harmonic generation in centrosymmetric graphene from quadrupole response.Yu Zhang#, Di Huang#, Yuwei Shan, Tao Jiang, Zhihong Zhang, Kaihui Liu, Lei Shi, Jinluo Cheng, John E. Sipe, Wei-Tao Liu*, Shiwei Wu*, Physical Review Letters 122, 047401 (2019)[6] Giant nonreciprocal second-harmonic generation from antiferromagnetic bilayer CrI3.Zeyuan Sun#, Yangfan Yi#, Tiancheng Song, Genevieve Clark, Bevin Huang, Yuwei Shan, Shuang Wu, Di Huang, Chunlei Gao, Zhanghai Chen, Michael McGuire, Ting Cao, Di Xiao, Wei-Tao Liu, Wang Yao, Xiaodong Xu* & Shiwei Wu*, Nature 572, 497–501 (2019).