Stability and properties of high-buckled two-dimensional tin and lead

TL;DR

This study investigates the stability and electronic properties of high-buckled two-dimensional tin and lead, revealing their metallic nature and potential for valleytronics applications due to unique valley and spin coupling.

Contribution

It demonstrates the stable high-buckled phase of 2D tin and lead and introduces fluorinated tin as a new platform for valleytronics with novel valley-spin coupling.

Findings

High-buckled phases are stable and metallic.

Fluorinated tin stabilizes small samples and exhibits unique valley-spin coupling.

These structures are unsuitable for topological fullerenes.

Abstract

In realizing practical non-trivial topological electronic phases stable structures need to be determined first. Tin and lead do stabilize an optimal two-dimensional high-buckled phase --a hexagonal-close packed bilayer structure with nine-fold atomic coordination-- and they do not stabilize topological fullerenes, as demonstrated by energetics, phonon dispersion curves, and the structural optimization of finite-size samples. The high-buckled phases are metallic due to their high atomic coordination. The optimal structure of fluorinated tin lacks three-fold symmetry and it stabilizes small samples too. It develops two oblate conical valleys on the first Brillouin zone coupling valley, sublattice, and spin degrees of freedom with a novel $\tau_z\sigma_xs_x$ term, thus making it a new 2D platform for valleytronics.