Dr.Pok-Man Chiu Abstract

Title: Emergence of Topological Phases and Their Transport Properties: From
2D to 3D, and Topology to Observable

Speaker: Dr.Pok-Man Chiu

Time: Oct. 22, 1:30 PM
Place: 理論中心4樓演講廳 (NCTS, 4F, lecture room)

Abstract:

Topology is a pure mathematical concept. Surprisingly, it also characters the properties of matters and can be easured by transport experiment. In this talk, I will emphasize the connection between the concept of topology and observable in experiment.

In the past ten years, more and more new topological phases had been discovered both experimentally and theoretically.In 2D systems, graphene is a well-known example and can be treated as a topological semimetal. In 3D systems,the topological phases are richer such as topological crystalline insulators, Weyl semimetals and nodal line semimetals.Although 2D and 3D systems share a large part of common topological phases, some topological phases only exist in 2D or 3D because of the topological constrained. Generally different phases were realized in different materials.Since there were many topological phases, there raises a question: can one generate different topological phases in a single-setup?

To answer this question, a stacking method was proposed. Using the method, we constructed four classes of 3D minimal models via vertically stacking a 2D nonsymmorphic lattice with and without breaking crystalline symmetries. As a result, four distinct topological phases can be generated in our minimal model, such as Dirac nodal line semimetals,
Weyl nodal line semimetals, unconventional Weyl semimetals with topological charge C = 2, and weak topological insulators.

This talk will be divided into two parts. In the first part, I will introduce the concept of topology and nonsymmorphic symmetry and demonstrate the topological phases in 2D and 3D. In the second part, their transport properties will be reported.

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