激子-声子耦合作用对单层过渡金属硫族化合物中

admin   2017-06-09 13:02:47   202

报告人: 王子武
报告时间:2017-06-14 15:30:00
报告地点:天津大学北洋园校区32楼B120

摘要:

  在单层过渡金属硫族等新型二维材料中,由于空间维度的受限和介电屏蔽效应导致体系中电子和空穴的强库仑相互作用,因此在这些层状材料中观察到了异常明显的激子效应和较大的激子结合能,这为激子物理和激子器件的研究提供了一个新的探索平台。针对这些单层材料,我们采用线性组合算符结合幺正变换的方法,理论研究了激子-声子耦合作用对激子结合能的修正,重点考虑了体纵光学声子和由极性衬底诱导出的表面光学声子两种耦合作用。理论发现:正是这些耦合作用导致了激子结合能的大幅度修正,这为实验测量激子结合能的不一致性提供了理论诠释和基础。另外,我们还将对层间和层内激子的最新实验和理论研究进展及其相应的器件设计进行概述。


Abstract:

The strong Coulomb interaction between electrons and holes is the most significant property of these monolayer materials arising from the reduced dimensionality and dielectric screening. This enhanced interaction leads to the formation of tightly bound excitons and large exciton binding energies, which implies rich excitonic physics in these monolayer materials. We theoretically investigate the correction of exciton binding energy arising from the exciton optical phonon coupling in monolayer transition metal dichalcogenides (TMDs) using the linear operator and Lee-Low-Pines unitary transformation methods. We take into account not only the exciton coupling with the intrinsic longitudinal optical (LO) phonon modes, but also the surface optical phonon modes induced by the polar substrates supporting monolayer TMDs. We find that the exciton binding energies are corrected in large scale due to these exciton-optical phonon couplings. We present the dependences of exciton binding energy on the cut-off wave vector of optical phonon modes, the polarization strength of substrate materials and the distance between polar substrates and TMDs. These results provide potential explanations for the discrepancy of the exciton binding energy between experiment and theory in TMDs. In addition, we will introduce the recent experimental and theoretical progress for the interlayer and intralayer excitons in these layered heterostructures.


  • 2009.09 - 2012.07  中国科学院半导体研究所和清华大学联合培养博士(凝聚态理论)
  • 2012.07 - 2013.10  中国科学院苏州纳米技术与纳米仿生研究所助理研究员
  • 2013.12 - 至今  天津大学理学院物理系