Accurate recipe for predicting valley Linear Weyl phonons in two dimensions

TL;DR

This paper provides a comprehensive method to identify valley Linear Weyl phonons in 2D materials by analyzing all 80 layer groups, identifying 11 candidate materials with specific symmetry properties.

Contribution

It offers an exhaustive symmetry-based search for valley LWP phonons in 2D systems and identifies specific 2D materials as candidates.

Findings

Valley LWP phonons can occur in 11 of 80 layer groups.

Identified 11 2D material candidates with valley LWP phonons.

Provided a symmetry-guided method for searching LWP phonons in 2D materials.

Abstract

The discovery of topological quantum states in two-dimensional (2D) systems is one of the most promising advancements in condensed matter physics. Linear Weyl point (LWP) phonons have been theoretically investigated in some 2D materials. Especially, Jin, Wang, and Xu [Nano Lett. 2018, 18, 12, 7755-7760] proposed in 2018 that the candidates with threefold rotational symmetry at the corners of the hexagonal Brillouin zone can host LWP phonons with a quantized valley Berry phase. However, all the candidates with hexagonal lattices may not host LWP phonons at $K$ ($K'$) high-symmetry points (HSPs). Hence, a more accurate recipe for LWP phonons in 2D is highly required. This work provides an exhaustive list of valley LWP phonons at HSPs in 2D by searching the entire 80 layer groups (LGs). We found that the valley LWP phonons can be obtained at HSPs in 11 of the 80 LGs. Guided by the symmetry analysis, we also contributed to realizing the ideal 2D material with valley LWP phonons. We identified the existence of the valley LWP phonons in eleven 2D material candidates with 11 LGs. This work offers a method to search for valley LWPs in 2D phononic systems and proposes 2D material candidates to obtain the valley LWP phonons.