Insight into the Topological Nodal Line Metal YB2 with Large Linear Energy Range: A First-Principles Study

Abstract

The presence of one-dimensional (1D) nodal lines, which are formed by band crossing points along a line in the momentum space of materials, is accompanied by several interesting features. However, in order to facilitate experimental detection of the band crossing point signatures, the materials must possess a large linear energy range around the band crossing points. In this work, we focused on a topological metal, YB2, with phase stability and a P6/mmm space group, and studied the phonon dispersion, electronic structure, and topological nodal line signatures via first principles. The computed results show that YB2 is a metallic material with one pair of closed nodal lines in the kz = 0 plane. Importantly, around the band crossing points, a large linear energy range in excess of 2 eV was observed, which was rarely reported in previous reports that focus on linear-crossing materials. Furthermore, YB2 has the following advantages: (1) An absence of a virtual frequency for phonon dispersion, (2) an obvious nontrivial surface state around the band crossing point, and (3) small spin–orbit coupling-induced gaps for the band crossing points.

Hexagonal Zr3X (X = Al, Ga, In) Metals: High Dynamic Stability, Nodal Loop, and Perfect Nodal Surface States

“…Based on the Brillouin zone and considered high-symmetry points Γ -M-K-Γ -A-L-H-A (as shown in Figure 1C), dynamic stability was examined for these three compounds according to the calculated phonon dispersions, and the results are given in Figures 1D, 2A,B, respectively. These Zr 3 X compounds are obviously dynamically stable due to the absence of the imaginary frequency (Han et al, 2019;Wu et al, 2019;Li et al, 2020a). These materials are therefore proposed to be experimental platforms to study topological semimetals/metals.…”