Research progress on topological nodal line semimetals

Topological quantum materials, such as topological insulators, topological semimetals, and topological superconductors, are the research focus of modern condensed matter physics and materials science. The purpose of this article is to give a brief introduction on the research progress of topological nodal line semimetal materials in recent years, and to focus on the latest research progress of our group in this field. Topological semimetals can be classified mainly by two aspects: Energy band degeneracy and dispersion. In terms of energy band degeneracy, this article will introduce nodal line semimetals protected by different symmetries including nodal line semimetals protected by symmorphic space groups and non-symmorphic space groups in the system with time reversion symmetry, and nodal line semimetals coupled with magnetic and topological orders without time reversion symmetry, respectively. In terms of energy band dispersion, this article will introduce high-order nodal line semimetals and type-II nodal line semimetals.