报告题目：𝐍𝐨𝐯𝐞𝐥 𝐌𝐞𝐭𝐚𝐥−𝐈𝐧𝐬𝐮𝐥𝐚𝐭𝐨𝐫 𝐓𝐫𝐚𝐧𝐬𝐢𝐭𝐢𝐨𝐧𝐬 𝐢𝐧 2D 𝐄𝐥𝐞𝐜𝐭𝐫𝐨𝐧 𝐆𝐚𝐬𝐞𝐬
报告时间：2019-12-27 14:00 (星期五)
报告地点：北洋园校区32教218室
报告人：王向荣 教授（香港科技大学）

报告人摘要： 

 Inthis talk, I will start with the conventional wisdom of the Andersonlocalization transitions.  Namely, allsystems can be classified into three ensembles: the Gaussian orthogonalensembles (GOE) when a system has both time-reversal and spin-rotational symmetries;the Gaussian unitary ensembles (GUE) when a system has neither time-reversalnor spin-rotational symmetries; and the Gaussian symplectic ensembles (GSE)when a system has time-reversal symmetry, but without spin-rotational symmetry.At the critical dimension of 2, no extended states exist in GOE at an arbitraryweak disorder, and extended states could exist in a GSE or a GUE when a strongperpendicular magnetic field is applied to drive the system into quantum Hallregion. Then I will argue the intrinsic inconsistency of this standardpicture.  It turns out that spin-orbitinteractions play a crucial role. The types of Anderson-localizationtransitions (metal-insulator transitions) in a two-dimensional system aresensitive to the types and strength of spin-orbit interactions. I will presentseveral simple models that support Berezinskii-Kosterlitz-Thouless typetransition from a band of localized states to a band of critical states; or aBerezinskii-Kosterlitz-Thouless type transition from a band of conventionalextended states to a band of critical states. In contrast to the conventionalwisdom, I will also provide the evidences that support the existence ofextended states in a GUE at a weak magnetic field.        

This work is supported by the NationalNatural Science Foundation of China (Grants No. 11774296 and 1974296) and HongKong RGC (Grants No. 16301518, 16301619 and 16300117). 

报告人简介 

王向荣，香港科技大学终身教授；1984年毕业于武汉大学物理系；1990年在美国罗彻斯特大学(Universityof Rochester)获博士学位。       

研究方向：凝聚态理论，研究领域包括量子霍尔效应，金属-绝缘体相变，超晶格以及磁动力学中；迄今已在国际权威学术杂志发表论文过百篇。