Ideal hourglass nodal loop state in the monolayer lithium hydrosulfide.

In recent years, the exploration of topological states within two-dimensional materials has emerged as a compelling focus, complementing their three-dimensional counterparts. Through theoretical calculations, we unveil the exceptional topological state in the monolayer lithium hydrosulfide, where an ideal hourglass nodal loop is identified. Notably, this nodal loop is characterized by only four bands, representing the simplest configuration for realizing hourglass dispersion.

Obvious Surface States Connecting to the Projected Triple Points in NaCl's Phonon Dispersion.

With the development of computer technology and theoretical chemistry, the speed and accuracy of first-principles calculations have significantly improved. Using first-principles calculations to predict new topological materials is a hot research topic in theoretical and computational chemistry. In this work, we focus on a well-known material, sodium chloride (NaCl), and propose that the triple point (TP), quadratic contact triple point (QCTP), linear and quadratic nodal lines can be found in the phonon dispersion of NaCl with Fm  m type structure.

Various Nodal Lines in P6/mmc-type TiTe Topological Metal and its (001) Surface State.

Searching for existing topological materials is a hot topic in quantum and computational chemistry. This study uncovers P6/mmc type TiTe compound-an existing material-is a newly discovered topological metal that hosts the various type of nodal line states. Different nodal line states normally exhibit different properties; they may have their individual applications.

Pure Zirconium: Type II Nodal Line and Nodal Surface States.

Type II nodal line states have novel properties, such as direction-reliant chiral anomalies and high anisotropic negative magneto-resistance. These type II nodal line states have been widely investigated. Compared to nodal line materials, there are far fewer proposed nodal surface materials, and furthermore, a very recent challenge is to find a realistic material that co-exhibits both nodal line and nodal surface states.