Electron-Correlation-Induced Charge Density Wave in FeGe

• Published in: Chinese physics letters Vol. 40; no. 11; pp. 117103 - 138
• Main Authors: Wu, Lin, Hu, Yating, Fan, Dongze, Wang, Di, Wan, Xiangang
• Format: Journal Article
• Language: English
• Published: Chinese Physical Society and IOP Publishing Ltd 01.11.2023
• ISSN: 0256-307X; 1741-3540; 1741-3540
• DOI: 10.1088/0256-307X/40/11/117103

As the first magnetic kagome material to exhibit the charge density wave (CDW) order, FeGe has attracted much attention in recent research. Similar to A V 3 Sb 5 ( A = K, Cs, Rb), FeGe exhibits the CDW pattern with an in-plane 2×2 structure and the existence of van Hove singularities near the Fermi level. However, sharply different from A V 3 Sb 5 which has phonon instability at M point, all the theoretically calculated phonon frequencies in FeGe remain positive. Based on first-principles calculations, we surprisingly find that the maximum of nesting function is at K point instead of M point. Two Fermi pockets with Fe- d xz and Fe- d x 2 – y 2 / d xy orbital characters have large contribution to the Fermi nesting, which evolve significantly with k z , indicating the highly three-dimensional (3D) feature of FeGe in contrast to A V 3 Sb 5 . Considering the effect of local Coulomb interaction, we reveal that the instability at K point is significantly suppressed due to the sublattice interference mechanism. Meanwhile, the wave functions nested by vector M have many ingredients located at the same Fe site, thus the instability at M point is enhanced. This indicates that the electron correlation, rather than electron-phonon interaction, plays a key role in the CDW transition at M point.