»ã±¨±êÌâ (Title)£ºQuasiparticle and Excitonic Properties from Few-Layer to Bulk GaSe£¨´ÓÉٲ㵽¿éÌåGaSeµÄ×¼Á£×Ӻͼ¤×ÓÐÔÖÊ£©

»ã±¨ÈË (Speaker)£º¼Ö·«ºÀ ÌØƸ¸±½ÌÊÚ£¨º¼Öݵç×ӿƼ¼´óѧ£©

»ã±¨¹¦·ò (Time)£º2023Äê12ÔÂ18ÈÕ(ÖÜÒ») 10:00

»ã±¨µØÖ· (Place)£ºÐ£±¾²¿ E106

Ô¼ÇëÈË (Inviter)£ºÈÎΰ ½ÌÊÚ

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ÌáÒª (Abstract)£º

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.