𝐍𝐨𝐯𝐞𝐥 𝐌𝐞𝐭𝐚𝐥−𝐈𝐧𝐬𝐮𝐥𝐚𝐭𝐨𝐫 𝐓𝐫𝐚𝐧𝐬𝐢𝐭𝐢𝐨𝐧𝐬 𝐢𝐧 2D 𝐄𝐥𝐞𝐜𝐭𝐫𝐨𝐧 𝐆𝐚𝐬𝐞𝐬

admin   2019-12-22 20:53:40   4001

报告题目:𝐍𝐨𝐯𝐞𝐥 𝐌𝐞𝐭𝐚𝐥−𝐈𝐧𝐬𝐮𝐥𝐚𝐭𝐨𝐫 𝐓𝐫𝐚𝐧𝐬𝐢𝐭𝐢𝐨𝐧𝐬 𝐢𝐧 2D 𝐄𝐥𝐞𝐜𝐭𝐫𝐨𝐧 𝐆𝐚𝐬𝐞𝐬
报告时间:2019-12-27 14:00 (星期五)
报告人:王向荣 教授(香港科技大学)


 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). 


王向荣,香港科技大学终身教授;1984年毕业于武汉大学long8唯一;1990年在美国罗彻斯特大学(Universityof Rochester)获博士学位。       



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