Quasiparticle characteristics of the weakly ferromagnetic Hund's metal MnSi

Abstract

Hund's metals are multi-orbital systems with $3d$ or $4d$ electrons exhibiting both itinerant character and local moments, and they feature Kondo-like screenings of local orbital and spin moments, with suppressed coherence temperature driven by Hund's coupling $J_H$. They often exhibit magnetic order at low temperature, but how the interaction between the Kondo-like screening and long-range magnetic order is manifested in the quasiparticle spectrum remains an open question. Here we present spectroscopic signature of such interaction in a Hund's metal candidate MnSi exhibiting weak ferromagnetism. Our photoemission measurements reveal renormalized quasiparticle bands near the Fermi level with strong momentum dependence: the ferromagnetism manifests through possibly exchange-split bands (Q1) below $T_C$ , while the spin/orbital screenings lead to gradual development of quasiparticles (Q2) upon cooling. Our results demonstrate how the characteristic spin/orbital coherence in a Hund's metal could coexist and compete with the magnetic order to form a weak itinerant ferromagnet, via quasiparticle bands that are well separated in momentum space and exhibit distinct temperature dependence. Our results imply that the competition between the spin/orbital screening and the magnetic order in a Hund's metal bears intriguing similarity to the Kondo lattice systems.

accepted by PRB

References in corpus (8)

• Strong electronic correlations from Hund's coupling
• Magnetism and Charge Dynamics in Iron Pnictides
• The coherence-incoherence crossover and the mass-renormalization puzzles in Sr2RuO4
• Observation of Temperature-Induced Crossover to an Orbital-Selective Mott Phase in A${}_x$Fe${}_{2-y}$Se${}_2$ (A=K, Rb) Superconductors
• Formation of a topological non-Fermi liquid in MnSi
• Symmetry-enforced topological nodal planes at the Fermi surface of a chiral magnet
• Orbital-differentiated coherence-incoherence crossover identified by photoemission spectroscopy in LiFeAs
• Revealing the Hidden Heavy Fermi Liquid in CaRuO3