时间：5月28日（周二）下午2:30-4:00

地点：物理馆323

於逸骏和陈国瑞两位博士将做两个报告，报告他们的最新进展：二维原子材料中的超导、铁磁态和石墨烯摩尔超晶格体系中的超导与拓扑量子态。

报告一: Controlling Electronic Properties of Correlated Two-Dimensional Materials

报告人: 於逸骏 博士, Fudan University

摘要: Vast opportunities exist in correlated Two-dimensional (2D) materials: they feature a number of exotic phenomena such as charge density waves (CDWs), high-temperature superconductivity (HTS) and magnetism. However, experimentally extracting monolayers from bulk correlated materials and control their electronic properties turned out to be extremely challenging. In this talk, I will introduce the fabrication and control technique we developed in the past years and interguing results we obtained in several 2D systems. In the model CDW material 1T-TaS₂, we are able to control the phase transitions by thinning it down to 2D limit or electrochemical gating. In itinerate magnet Fe₃GeTe₂, we observe intrinsic ferromagnetism in 2D limit and the Curie temperature can be turned up to room temperature. In monolayer high-temperature superconductor Bi₂Sr₂CaCu₂O_8+x, we obtain a phase diagram lack of dimensionality effect, which indicates that monolayer cuprate contains all essential physics of HTS.

报告二: Tunable strongly correlated and topological phenomena in trilayer graphene on boron nitride moiré superlattice

报告人: 陈国瑞 博士，UC Berkeley & LBNL

摘要：Mott insulator is a central concept in strongly correlated physics and manifests when the repulsive Coulomb interaction between electrons dominates over their kinetic energy. A tunable Mott insulator, where the competition between the Coulomb interaction and the kinetic energy can be varied in situ, can provide an invaluable model system for the study of Mott physics. In this talk, I will discuss a general route to engineer strongly correlated physics in two-dimensional moiré superlattices, and show the experimental realization of a tunable Mott insulator in the ABC stacked trilayer graphene (TLG)/hBN moiré superlattice.The moiré superlattice in TLG/hBN heterostructures leads to narrow electronic minibands and allows for the observation of gate-tunable Mott insulator states at 1/4 and 1/2 fillings. Interesting signatures of superconductivity are observed at low temperature near the 1/4 filling Mott insulating state in the TLG/hBN heterostructures. A topological Chern insulator with Chern number C=2 and ferromagnetism is experimentally observed in the non-trivial band in trilayer graphene system, which makes it possible to study Mott, superconductivity and topological physics in one system.