$T_{3}$Pb$_{2}Ch_{2}$ ($T$=Pd,Pt and $Ch$=S,Se) with transition metal kagome net: Dynamical properties, phonon nodal line, phonon surface states, and chiral phonons

Abstract

Shandite with Ni3Pb2S2 chemical formula and R 3m symmetry, contains the kagome sublattice formed by the transition metal atoms. Recent experimental results confirmed the possibility of successfully synthesizing Pd3Pb2Ch2 (Ch=S,Se) with the same structure. In this paper, we theoretically investigate the dynamical properties of such compounds. Furthermore, we study the possibility of realizing Pt3Pb2Ch2 with the shandite structure. We show that the Pd3Pb2Ch2 and Pt3Pb2S2 are stable with R 3m symmetry. In the case of Pt3Pb2S2, there is a soft mode, which is the source of the structural phase transition from R 3m to R 3c symmetry, related to the distortion within the kagome sublattice. We discuss realized phonon nodal lines in the bulk phonon dispersions in upper frequency modes. We show that the shandite structure can host the phonon surface states, with strong dependence by the surface kind. Additionally, chiral phonons with circular motion of the Pb atoms around the equilibrium position are realized.

Impact of M‐Site Cation Variation on Structural, Electronic, and Optical Properties of Pd3M2Se2 (M = Pb, Sn) Dichalcogenides: A Computational Study

“…Surajit Basak et al recently confirms the experimental synthesis of the Pd 3 Pb 2 Se 2 shandite with space group R-3m. [46] Figure 1(c) illustrates the Kagome lattice of Pd which constitutes the Pd 3 M 2 Se 2 combination. According to their positioning, the M-Site metal cation may be categorized into two kinds: M1 and M2.…”