Title:Magnetism of fermions on triangular lattice

Speaker: HE Yuchi，University of Ghent

Time:2024-12-4 14：00  

Venue:W316，Physics Building

Abstract:The investigation of twisted bilayer graphene has opened a “twistronics era”, providing unprecedented tunability for solid-state systems and an excellent platform for strongly correlated quantum phases and their transitions. While twisted bilayer graphene requires involved multi-band descriptions, twisted bilayer transition metal dichalcogenides are simpler. In this talk, I will introduce some of our theoretical works related to recent experimental progress. We studied two cases of twisted bilayer transition metal dichalcogenides: (1) effective triangular systems and (2) effective honeycomb systems. For triangular systems, we predict magnetic orders and spin liquids at half-filling; we study the magnetic orders at the van Hove filling, predicting rich metallic magnetic orders. To gain some understanding of magnetism in the case away from half-filling. We use a cluster construction at 1/3 doping and  analyze the competing antiferromagnetic and ferromagnetic exchange interactions from different virtual processes. The model we construct supports antiferromagnetism for intermediate interaction and  ferromagnetism at strong interactions.

Bio:Yuchi He obtained his PhD in the physics department of Carnegie Mellon University, USA in 2020. Before that, he earned his BS from Peking University. He worked as a postdoc at RWTH Aachen University and the University of Oxford. Now he is a postdoc at Ghent University and a visiting researcher at Oxford.  His primary research interest is phases and dynamics of strongly correlated quantum many-body systems. One-dimensional and two-dimensional systems are investigated by applying and developing effective theory and tensor network methods.