报告题目 (Title)：Quasiparticle and Excitonic Properties from Few-Layer to Bulk GaSe（从少层到块体GaSe的准粒子和激子性质）

报告人 (Speaker)：贾帆豪 特聘副教授（杭州电子科技大学）

报告时间 (Time)：2023年12月18日(周一) 10:00

报告地点 (Place)：校本部 E106

邀请人 (Inviter)：任伟 教授

主办部门：理学院物理系

摘要 (Abstract)：

Metal monochalcogenide GaSe is a classic layered semiconductor that has received increasing research interest in modern ultrathin electronics. In this work, we performed GW plus Bethe-Salpeter equation (BSE) calculations from monolayer, few-layer to bulk systems to provide a continuous understanding of its layer-dependent quasiparticle and optical properties and reconcile present mixed experimental measurements. The interlayer coupling greatly suppresses the interesting Mexican-hat-like dispersion in the top valence band but enhances the valence band splitting as the number of layers increases. The significantly varying dielectric screening effects are responsible for their distinct quasiparticle band gaps and excitonic structures. Detailed examinations reveal that bulk excitons can exhibit large binding energies comparable to those of few-layers owing to exciton wave function localization. Compared to the change in absorption spectrum from bilayer to bulk, the change from monolayer to bilayer is much more significant. The internal structure of the excitonic states was investigated to elucidate several important underlying characteristics of these changes.