Past Events

Abstract

Recently, topological properties contained in condense matter systems have drew more and more attention to both theoretical and experimental physicists. As a simple system, liquid³He provides us with a pedagogical and representative example to show the relationship between the topological properties of Fermionic vacua in momentum space and its co-dimension. In this lecture, I will firstly study the microscopic physics of liquid³He and give the energy spectrum of it. Then following symmetry breaking scheme, different phases together with relevant Fermionic vacua of liquid³He are provided. Next using homotopy group theory and momentum space topology, we thoroughly study the stability of different fermionic vacua and define corresponding winding numbers of them. When considering discrete symmetries of different phases, there are other kinds of topological charges we can define to characterize different phases. Finally we refer to the famous periodic table of classification of momentum space topology and propose several interesting questions to be studied in future.