报告题目：Valleys and angular momentum of excitons trapped in a moiré potential

报告时间：2025年5月29日（周四）15:30

报告地点：鼓楼校区唐仲英楼 B501

报  告 人：Jun Yan，University of Massachusetts Amherst

摘      要：

Moiré structures, formed by stacking two atomically thin crystals with slightly different lattice constant or orientation, are complicated looking in real space as the atomic registry modulates over many different configurations in the cell.  Surprisingly, experiments show that the angular momentum of exciton emission in the system are well defined, inherited from the valley properties of the monolayer crystal, and assisted by lattice reconstruction that nature kindly offers. This talk will introduce valley properties of the monolayers and discuss how the ideas are applied and modified to describe the excitons in a moiré lattice. The moiré excitons display an unusual valley polarization behavior, impacted by population of two-exciton states and Coulomb interaction that can be tuned by an external magnetic field, highly distinct from the monolayer samples.

References:

1. Yueh-Chun Wu, et al 'Highly tunable valley polarization of potential-trapped moiré excitons in WSe₂/WS₂ heterojunctions' arXiv:2503.06299 Phys. Rev. Lett. in press.

报告人简介：

Jun Yan is an Associate Professor of Physics at the University of Massachusetts Amherst, where his research focuses on the optical and optoelectronic properties of atomically thin crystals and quantum materials. Dr. Yan completed his undergraduate studies at Nanjing University and earned his PhD at Columbia University. Under the supervision of Prof. Aron Pinczuk and Prof. Philip Kim at Columbia, he pioneered Raman scattering studies of electron-phonon coupling effects in graphene. In 2009, Dr. Yan joined Prof. Michael Fuhrer’s group at the University of Maryland, College Park, as a postdoctoral researcher. There, he conducted charge transport studies of graphene and developed ultrasensitive photo-detectors based on graphene. Since joining the faculty at UMass Amherst in 2012, Dr. Yan has further advanced graphene detectors for sensing TeraHertz radiation, and developed versatile optical spectroscopy techniques to study quantum materials and two-dimensional atomic layers, such as transition metal dichalcogenide semiconductors, with an emphasis on Coulomb interactions and symmetry effects.