Encoding innumerable charge density waves of FeGe into polymorphs of LiFe6Ge6

TL;DR

This paper demonstrates how metastable charge density waves in FeGe can be mapped onto stable polymorphs of LiFe6Ge6, revealing a new route to structural polymorphism and enabling exploration of kagome magnet physics.

Contribution

It introduces a novel mechanism linking charge density waves in FeGe to stable polymorphs of LiFe6Ge6, expanding the understanding of structural diversity in kagome magnetic materials.

Findings

Infinite metastable CDWs in FeGe due to Ge1-dimerization arrangements

Stable polymorphs of LiFe6Ge6 stabilized by filling Li atoms in CDW superstructures

Fingerprint features of CDWs encoded in LiFe6Ge6 polymorphs

Abstract

Kagome metals exhibit rich quantum states by the intertwining of lattice, charge, orbital and spin degrees of freedom. Recently, a novel charge density wave (CDW) ground state was discovered in kagome magnet FeGe and was revealed to be driven by lowering magnetic energy via large Ge1-dimerization. Here, based on DFT calculations, we show that such mechanism will yield infinitely many metastable CDWs in FeGe due to different ways to arrange the Ge1-dimerization in enlarged superstructures. Intriguingly, utilizing these metastable CDWs, innumerable polymorphs of kagome magnet LiFe6Ge6 can be stabilized by filling Li atoms in the voids right above/below the dimerized Ge1-sites in the CDW superstructures. Such polymorphs are very stable due to the presence of magnetic-energy-saving mechanism, in sharp contrast to the non-magnetic "166" kagome compounds. In this way, a one-to-one mapping of the metastable CDWs of FeGe to stable polymorphs of LiFe6Ge6 is established. On one hand, the fingerprints of these metastable CDWs, i.e., the induced in-plane atomic distortions and band gaps, are encoded into the corresponding stable polymorphs of LiFe6Ge6, such that further study of their properties becomes possible. On the other hand, such innumerable polymorphs of LiFe6Ge6 offer great degrees of freedom to explore the rich physics of magnetic kagome metals. We thus reveal a novel connection between the unusually abundant CDWs and structural polymorphism in magnetic kagome materials, and establish a new route to obtain structural polymorphism on top of CDW states.