题目：Plateau transitions in Quantum Hall Effect: Role of edge states,Topological Insulators and 3D Ising model.

报告人：Ara Sedrakyan  (Alikhanyan National Science Laboratory,Yerevan,Armenia)

时间：4月3日, 10：00-11：30

地点：李薰楼249室

Abstract:

There will be three talks on plateau-plateau transition problem in Integer Quantum Hall effect (IQHE):

1. Introduction to IQHE. We will reveal how edge states appear in IQHE,their role in quantization of Hall conductivity and in contributing to Ohm (longitudinal) conductivity.

2.  Plateau transitions in IQHE, appearance of longitudinal conductivity due to edge states. I will present a single-parameter family of random network models of edge states for plateau transitions, where the localization length indexes are calculated and compared against experimental data. Network model is formulated as a network of scattering electrons, where the nodes are randomly distributed in real space. For the particular value of the parameter, p=1/3, the calculated value of the localization length index coincides with the experimental value on GaAs. 

3. The model also can be used to describe the QHE in topological insulators,and it is argued,that the parameter p is linked to the compensation parameter K=N_A/N_D,leading to the varying value of the localization length index. We will present a suggestion for the experiment. Statistical properties of the random network

Ara Sedrakyan  

Ph.D. in Theoretical Physics, 1978, Yerevan Physics Institute. 

Doctor of Science, 1989, Yerevan Physics Institute.

Since 1989， He has been a full Professor at the Yerevan Physics Institute. 

He has held numerous visiting professorships at various top-level European and US institutions, including the Niels Bohr Institute in Copenhagen, Denmark; LAPTH in Annecy, France; Freie University in Berlin, Germany; ISSP at Tokyo University, Japan; the University of Chicago; the University of Wuppertal, University of Augsburg, Germany and Complutense University of Madrid, Spain.

He is an expert in non-critical string theory, in particular, string formulation of the 3D Ising model. Over the last 15 years, he has been working on the problem of Plateau transitions in QHE, Integrable models in 2D and 3D and on Symmetry Protected Topological phase transitions.