Halogen Chains with One-Dimensional Semi-Metallic Electronic Structure and Peierls Physics in Polymorphs of Na4X5 (X = I, Br, Cl) Compounds

TL;DR

This study demonstrates a novel experimental approach to synthesize monoatomic one-dimensional halogen chains within sodium halide compounds, revealing Peierls physics and semi-metallic electronic structures through combined synthesis and theoretical analysis.

Contribution

It introduces a new method for stabilizing one-dimensional halogen chains in ionic compounds, advancing the understanding of Peierls physics in these systems.

Findings

Successful synthesis of incommensurately modulated Na4X5 compounds.

Confirmation of Peierls physics via theoretical calculations.

Discovery of new Na4Cl5 and Na4Br5 phases with one-dimensional electronic structures.

Abstract

Since the pioneering works of Peierls, one-dimensional materials have attracted great attention. Still, the synthesis of truly monoatomic chains remains elusive. In this study, we explore a novel path of experimental synthesis of monoatomic one-dimensional chains by their chemical stabilization in ionic compounds. We demonstrate that in synthesized at high pressure sodium halides Na4X5 (X = I, Br, Cl) with hP18 Ga4Ti5-type structures, transfer of valence electrons from cations to anions leads to the formation of halogen chains connected with other atoms only by ionic interaction and having one-dimensional electronic structure. The Peierls physics in the systems is confirmed by theoretical calculations, newly synthesized incommensurately modulated i-hP18-Na4X5 (X = I, Br, Cl) compounds, as well as by the discovered hP36 phases of Na4Cl5 and Na4Br5.