报告题目(中文)：Non-covalent interlayer interactions: visualization, magnetic coupling and Moir?patterns

报告内容简介：Van der Waals (vdW) interactions were believed dominant for interlayer interactions in layered two-dimensional (2D) materials. We recently found an emergent type of interlayer interactions, namely covalent-like quasi-bonding (CLQB) [1,2], in various 2D materials like black phosphorus [1,2], PtS2 [3], PtSe2 [4] and few-layer Te [5]. This interlayer interaction is, most likely, directly observed in TiS2 by x-ray scattering [6,7]. Such technique also suggested charge accumulation in hydrogen bonds, as we imaged by a qPlus non-contact Atomic Force Microscope with a CO terminated tip [8], which suggests a covalent characteristic of hydrogen bonds. However, it was argued that the contrast between molecules is a result of CO tip tilting [9], which boost extensive discussions in the field. In collaboration with our experimental and theoretical coworkers [10], we found an O atom modified Cu tip is of strong lateral stability which is an order of magnitude higher than the usual CO modified tip. In addition, we employed first-principles density functional theory calculations to reveal the interlayer magnetic coupling mechanism at the vdW gaps of CrI3 [11], CrS2 [12] and CrSe2 [13] bilayers. We found an orbital dependent magnetic coupling mechanism in CrI3 and predict that different interlayer orbital interactions led by different stacking orders result in interlayer ferro and anti-ferro-magnetic couplings. In addition, we found a Bethe-Slater-curve-like relation between magnetic coupling and interlayer distance in CrSe2 and its analogues. A double-super-exchange mechanism was proposed to understand such BSC-like behavior. In the last part, I briefly discuss emerging electronic states in vdW hetero-bilayers, like MoS2/WSe2 and MoSe2/PtSe2 where interlayer electronic hybridization results in new gap states at the interfaces [14]. References [1] J. Qiao et al. Nature Communications 5, 4475 (2014) [2] Z.-X. Hu et al. Nanoscale 8, 2740 (2016). [3] Y. Zhao et al. Advanced Materials 28, 2399-2407 (2016). [4] Y. Zhao et al. Advanced Materials 29, 1604230 (2017). [5] J. Qiao et al. Science Bulletin 63, 159-168 (2018). [6] H. Kasai et al. Nature Materials 17, 249-252 (2018). [7] X. Qiu and W. Ji Nature Materials 17, 211-213 (2018). [8] J. Zhang et al. Science 342, 611-614 (2013). [9] S. K. H鋗鋖鋓nen et al. Physical Review Letters 113, 186102 (2014). [10] H. M鰊ig et al. Nature Nanotechnology 13, 371-375 (2018). [11] P. Jiang and C. Wang et al. Physical Review B 99, 144401 (2019 ) arXiv:1806.09274 [12] C. Wang, et al. Physical Review B 97, 245409 (2018) [13] X. Zhou, et al., arXiv:1906:05576 (2019) [14] J. Zhou, et al. ACS NANO, ASAP, DOI:10.1021/acsnano.8b09479 (2019)

报告人姓名：季威

报告人简介(中文)：Dr. Ji, Wei is a computational physicist, working in the field of surface and interface modeling of low-dimensional materials. His research interests include surface and interface modeling of emerging electronic materials and devices. Recently, he focuses on theoretical modeling of electronic, optical, and vibrational properties of two-dimensional materials. He has been also developing theoretical methods for describing beam effects in scanning transmission microscopy and understanding ultrahigh resolution in noncontact atomic force microscopy. He received his Ph.D in condensed matter physics from the Institute of Physics, Chinese Academy of Science in 2008. Prior to joining Renmin University of China, he spent four years in McGill University as a visiting scholar and then a postdoctoral fellow. He was originally appointed as an Associated Professor by Renmin University in 2010 and was early promoted to Full Professor in 2014. He was supported by the National Young Top-Notch Talent Program in 2014, the National Science Fund for Excellent Young Scholars in 2016 and awarded Chang-Jiang Young Scholars in 2015. He also serves as an Associated Editor of ACS Applied Electronic Materials, an Editorial Board Member of Science Bulletin and trustees in the youth committee and computational materials science division of the Chinese Materials Research Society.

报告人单位(中文)：中国人民大学物理系

报告时间：2019-10-21 15:30

报告地点：上大东区材料楼B楼520会议室

主办单位：上海大学材料学院

联系人：施思齐