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

Time: Friday 15:00–16:30, every week from March 13 to April 17

Venue: Room 468, Lee Hsun Building, IMR CAS

There will be six lectures covering the quantum Hall effect, with a focus on the role of edge states in plateau-plateau transitions and the broader topological properties of matter. The series will also explore how these topological features connect to magnetism and electronic transport.

This six-lecture series will examine:

1. Classical Hall effect. Drude theory.

2. The quantum Hall effect (QHE).

The quantization, Landau levels, and physical intuition. Integer and fractional regimes of QHE.

3. Correspondence of clasical and quantum HE. Quasi-classical approximation.

4. Edge states and transport

How chiral edge modes arise, their role in current flow, and their importance in plateau–plateau transitions.

5. Topological properties of matter. Network Model for plateau-plateau transitions.

Berry phase, Chern numbers, and topological invariants relevant to magnetotransport.

6. Connections to magnetism and condensedmatter systems

How magnetic fields produce topologically nontrivial electronic phases and how these affect observable transport phenomena.

Abstract:

This six-lecture series explores the quantum Hall effect as a paradigmatic example of topology in condensed matter systems, with particular emphasis on the role of edge states in plateau–plateau transitions and the broader topological structure of matter.

We begin with the foundational physics of Landau quantization, disorder, and localization underlying the integer and fractional quantum Hall effects. The quantization of Hall conductance will be formulated in terms of topological invariants, including Chern numbers and Berry curvature, establishing the deep connection between bulk topology and measurable transport coefficients.

A central focus of the series will be the physics of edge states and the bulk–boundary correspondence. We will examine how chiral edge modes govern charge transport and how their evolution, together with the delocalization of bulk states, controls plateau–plateau transitions and universal critical scaling behavior.

The lectures will further situate quantum Hall systems within the wider framework of topological phases of matter, including Chern insulators and magnetic topological materials. Particular attention will be given to the interplay between topology, magnetism, and electronic transport, highlighting how magnetic order, symmetry breaking, and interactions reshape topological protection and transport phenomena.

Ara Sedrakyan  

Ph.D. in Theoretical Physiscs, 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.