报告题目：Salient physics of transition metal dichalcogenides
报告人：张绳百教授 美国伦斯勒理工学院
报告时间：2016年11月30日 上午10:00点
报告地点：北航四号楼205会议室
报告摘要：
Materials physics of two-dimensional (2D) semiconductors can be noticeably different from that of traditional three-dimensional semiconductors, both in standard and in 2D-specific properties. Taking transition metal dichalcogenides (TMDs) as an example: while a semiconductor surface tends to reconstruct according to the electron counting model (ECM) [1], the same model does not apply to TMD. More intriguingly, first-principles calculations reveal that the multi-valency of transition metal element can be critically important to the edge reconstruction [2]. The latter is vital for the understanding of strong photoluminescence observed in MoS2 flakes [3]. The MoS2 can also be stacked with WS2 to form an atomically-thin heterostructure from which experiment has observed a ultrafast femtosecond hole transfer upon optical excitation [4]. Using the time-dependent DFT approach coupled with molecular dynamics, we propose that the collective motion of excited carriers could be responsible for the ultrafast dynamics [5]. For such a van der Waals interface, charge transfer is also a matter of criticality where the timescale of the transfer varies discontinuously (from very fast to very slow) with respect to the interfacial dipole coupling.
[1] M. D. Pashley, Phys. Rev. B 40, 10481 (1989).
[2] M. C. Lucking, J. Bang, H. Terrones, Y.-Y. Sun, and S. Zhang, Chem. Mater. 27, 3326 (2015). [3] H. R. Gutiérrez, et al., Nano Lett. 13, 3447 (2012).
[4] X. Hong, et al., Nat. Nanotech. 9, 682 (2014); Y. Yu, et al., Nano Lett. 15, 486 (2015).
[5] H. Wang, J. Bang, Y. Sun, L. Liang, D. West, V. Meunier, and S. Zhang, Nat. Comm. 7, 11504 (2016).
报告人简介：
张绳百教授于1981年获得加州大学伯克利分校物理博士学位，曾任美国可再生能源国家实验室教授，现任美国伦斯勒理工学院物理系教授，是该校十几位Kodosky星群教授之一。2001年入选美国物理学会会士。
张绳百教授的主要研究领域是材料的跨尺度计算，研究方向涉及光伏能源材料、相变存储材料、拓扑材料和二维层状材料等。目前已经发表论文200多篇，包括57篇PRL，5篇JACS、4篇Nature Communications、3篇PNAS和11篇Nano Letters，他引15176次，h因子62。
