Enhancement of charge instabilities in Hund's metals by the breaking of rotational symmetry

Abstract

We analyze multi-orbital Hubbard models describing Hund's metals, focusing on the ubiquitous occurrence of a charge instability, signalled by a divergent/negative electronic compressibility, in a range of doping from the half-filled Mott insulator corresponding to the frontier between Hund's and normal metals. We show that the breaking of rotational invariance favors this instability: both spin-anisotropy in the interaction and crystal-field splitting among the orbitals make the instability zone extend to larger dopings, making it relevant for real materials like iron-based superconductors. These observations help us build a coherent picture of the occurrence and extent of this instability. We trace it back to the partial freezing of the local degrees of freedom in the Hund's metal, which reduces the allowed local configurations and thus the quasiparticle itinerancy. The abruptness of the unfreezing happening at the Hund's metal frontier can be directly connected to a rapid change in the electronic kinetic energy and thus to the enhancement and divergence of the compressibility.

arXiv comment16 pages, 11 figures

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Cited by in corpus (12)

• Differentiating Hund from Mott physics in a three-band Hubbard-Hund model: Temperature dependence of spectral, transport, and thermodynamic properties
• Mott Quantum Critical Points at finite doping
• Extended regime of coexisting metallic and insulating phases in a two-orbital electronic system
• Hund's metal crossover and superconductivity in the 111 family of iron-based superconductors
• Charge disproportionation and Hund's insulating behavior in a five-orbital Hubbard model applicable to $d^4$ perovskites
• Slave-spin mean field for broken-symmetry states: Néel antiferromagnetism and its phase separation in multi-orbital Hubbard models
• Multipolar nematic state of nonmagnetic FeSe based on the DFT+$U$
• Thermodynamic Stability at the Two-Particle Level
• Accurate modeling of FeSe with screened Fock exchange and Hund's metal correlations
• Fingerprints of a charge ice state in the doped Mott insulator Nb${}_3$Cl${}_8$
• Rationalizing doping and electronic correlations in LaFe${}_2$As${}_2$
• Magnetically-induced local lattice anomalies and low-frequency nematic fluctuations in the Mott insulator La${}_2$O${}_3$Fe${}_2$Se${}_2$