Reza Asgari. Weyl Semimetals : New quantum phase in crystal (IRSAMC - 9 avril 2018)

lundi  9 avril 2018 : 14h30

Reza Asgari
School of Physics, Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5531, Iran
School of Nano Science, Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5531, Iran

LIEU  : Salle de séminaire, IRSAMC - Bat. IIIr1-B4 - 3ème étage
DATE  : 9 Avril 2018, 14 H 30

Summary

Condensed matter physics is a branch of physics tries to characterize phases of matter. Some phases can be understood in terms of the symmetries. Recently, it has become apparent that there can exist a more subtle kind of order in the pattern of entanglement in a quantum ground state in which symmetries preserve but they have fundamental properties that are insensitive to smooth changes in materials parameters. These properties can be understood as consequences of the topological structure of the quantum state.

In the first part of the talk, we will provide an introduction to the foundations of topological band theory and explain how these ideas can be used to characterize topological insulators. In the second part, we will focus on topological semimetals, which are free fermion phases where the energy gap closes at certain points in the Brillouin zone. We will focus mainly on the three-dimensional Weyl semimetal and its unusual surface states that take the form of Fermi arcs as well as its topological response. The low-energy excitations of this state are modeled by the Weyl equation of particle physics.

Finally, we will discuss our recent work on coupling phonon-electromagnetic waves in strained Weyl semimetals in which we describe the charge anomaly in the system. Having calculated the elastic and particle stress tensors, we obtain the dispersions of the optical and acoustic phonon modes in the presence of the electromagnetic waves.


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