Spin-charge-lattice coupling across the charge density wave transition in a Kagome lattice antiferromagnet

Abstract

Understanding spin and lattice excitations in a metallic magnetic ordered system form the basis to unveil the magnetic and lattice exchange couplings and their interactions with itinerant electrons. Kagome lattice antiferromagnet FeGe is interesting because it displays rare charge density wave (CDW) deep inside the antiferromagnetic ordered phase that interacts with the magnetic order. We use neutron scattering to study the evolution of spin and lattice excitations across the CDW transition $T_{\mathrm{CDW}}$ in FeGe. While spin excitations below $\sim$100 meV can be well described by spin waves of a spin-1 Heisenberg Hamiltonian, spin excitations at higher energies are centered around the Brillouin zone boundary and extend up to $\sim 180$ meV consistent with quasiparticle excitations across spin-polarized electron-hole Fermi surfaces. Furthermore, $c$-axis spin wave dispersion and Fe-Ge optical phonon modes show a clear hardening below $T_{\mathrm{CDW}}$ due to spin-charge-lattice coupling but with no evidence for a phonon Kohn anomaly. By comparing our experimental results with density functional theory calculations in absolute units, we conclude that FeGe is a Hund's metal in the intermediate correlated regime where magnetism has contributions from both itinerant and localized electrons arising from spin polarized electronic bands near the Fermi level.

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Cited by in corpus (11)

• Spin Excitations and Flat Electronic Bands in a Cr-based Kagome Superconductor
• Charge Dynamics of an Unconventional Three-Dimensional Charge Density Wave in Kagome FeGe
• Electronic band structures of topological kagome materials
• Frustrated charge density wave and quasi-long-range bond-orientational order in the magnetic kagome FeGe
• Disordered charge density waves in the kagome metal FeGe
• Vacancy-induced suppression of CDW order and its impact on magnetic order in kagome antiferromagnet FeGe
• Interplay of Charge Density Wave and Magnetism on the Kagomé Lattice
• Interacting spin and charge density waves in kagome metal FeGe
• Beyond kagome: $p$-bands in kagome metals
• Theory of unconventional magnetism in a Cu-based kagome metal
• Thermoelectric evidence of the electronic structure changes from the charge-density-wave transition in FeGe