理学院数理讲坛（2018年第39讲）
报告题目：Interlayer engineering in tuning physical properties of two-dimensional materials
报 告 人：季威 优青/青年
单 位：中国人民大学
报告时间：2018年9月28日（星期五9:00）
报告地点：龙赛理科楼 116
报告摘要：
Van der Waals forces 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 Te [5] few-layers. The existence of CLQB in Te allows to tune various Te phases from its bulk form (the alpha-phase) upon charge doping or external strain [6]. In addition to the known beta and gamma phases, At least three new phases, namely, delta, epsilon and zeta phases was found during charge doping and sliding of layers [7]. Among these phase, the alpha to gamma phases are semiconducting and the rest are metallic. In light of this, it might be a promising strategy to build all-Te electrical devices, since Te has both semiconducting and metallic phases, which show considerable stability and rather high carrier conductance. In addition, we discussed the interlayer magnetic couplings (IMC) of CrS2 and CrI3 bilayers. It is interesting that these two materials are at two extremes of IMC. The interlayer FM coupling in CrS2 is very robust and is nearly unable to be tuned under usual external fields, but the intra-layer magnetism does be varied under layer stacking [8]. An opposite case was found in CrI3 bilayers [9] where the intra-layer FM coupling is, however, very strong but the interlayer magnetism was found governed by a subtle change of interlayer stacking; this shows a decoupled magnetic interaction between intra- and inter-layer directions.
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] C. Wang, et al. arXiv:1806.06550
[7] C. Wang and L. Zhou et al. in preparation.
[8] C. Wang, et al. Phys. Rev. B 97, 245409 (2018), arXiv:1706.10213
[9] P. Jiang and C. Wang et al. arXiv:1806.09274
报告人简介：
季威博士长期专注于发展和应用独特的第一性原理计算方法，研究了多种表面量子系统和信息材料与器件界面等领域的前沿问题。他最近的研究兴趣主要集中在二维材料多种物性的理论模拟和调控策略方面。同时，他也在发展一些理论方法用于描述透射电子显微镜中的射线效应和非接触原子力显微镜中的高分辨成像机理。季威博士于2008年3月在中国科学院物理研究所获得博士学位，从2006年起在麦吉尔大学物理系做访问学者和博士后研究，随后于2010年加入中国人民大学物理系任副教授，并在2014年晋升教授。目前，他已经发表论文80余篇，被引3000余次，包括9篇ESI高被引论文和2篇ESI热点论文。这些研究成果入选2013中国科学十大进展、2014年、2015年中国百篇最具影响国际学术论文。此外，他2011年入选了教育部新世纪优秀人才支持计划、当选中国材料研究学会青委会理事；2014年入选中组部专家青年拔尖人才；2015年入选教育部奖励计划青年学者；2016年获得优秀青年科学基金支持、担任中国材料研究学会计算材料专业委员会委员。