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Speaker : Prof. James Hone Affiliation : Department of Mechanical Engineering, Columbia University Region : Americas Year : 2022 Language : English Van der Waals heterostructures, in which different two-dimensional (2D) materials are assembled into layered structures, provide a new opportunity to create tailor-made materials with new properties. Importantly, these properties are a function not only of the constituent materials but also the relative angle between the layers – leading to the new concept of ‘twistronics’. The ultra-low friction between layers in these heterostructures provides a unique opportunity to create tunable materials whose properties can be changed by modifying the interlayer twist angle. To do this, we rotate the top layer of a heterostructure using a contact-mode atomic force microscope (AFM) to modify the interfacial twist angle and moirè wavelength, modifying a number of emergent properties. In this talk I will describe three applications of this technique: (1) tuning bandstructure in graphene-hBN interfaces1; (2) tuning symmetry in graphene with two hBN layers2; and tuning the nonlinear response of hBN-hBN interfaces3. I will also describe new efforts to use on-chip electrostatic actuation to control rotation. 1. Ribeiro-Palau, R., C.J. Zhang, K. Watanabe, T. Taniguchi, J. Hone, and C.R. Dean, "Twistable electronics with dynamically rotatable heterostructures", Science 361, 690 (2018). 2. Finney, N.R., M. Yankowitz, L. Muraleetharan, K. Watanabe, T. Taniguchi, C.R. Dean, and J. Hone, "Tunable crystal symmetry in graphene-boron nitride heterostructures with coexisting moire superlattices", Nature Nanotechnology 14, 1029 (2019). 3. Kaiyuan Yao, Nathan R. Finney, Jin Zhang, Samuel L. Moore, Lede Xian, Nicolas Tancogne-Dejean, Fang Liu, Jenny Ardelean, Xinyi Xu, Dorri Halbertal, K. Watanabe, T. Taniguchi, Hector Ochoa, Ana Asenjo-Garcia, Xiaoyang Zhu, D. N. Basov, Angel Rubio, Cory R. Dean, James Hone, P. James Schuck, “Enhanced tunable second harmonic generation from twistable interfaces and vertical superlattices in boron nitride homostructures”, Science Advances 7, eabe8691 (2021)