Spin-state Crossover Model for the Magnetism of Iron Pnictides

Abstract

We propose a minimal model describing magnetic behavior of Fe-based superconductors. The key ingredient of the model is a dynamical mixing of quasi-degenerate spin states of Fe2+ ion by intersite electron hoppings, resulting in an effective local spin Seff. The moments Seff tend to form singlet pairs, and may condense into a spin nematic phase due to the emergent biquadratic exchange couplings. The long-range ordered part m of Seff varies widely, 0<=m<=Seff, but magnon spectra are universal and scale with Seff, resolving the puzzle of large but fluctuating Fe-moments. Unusual temperature dependences of a local moment and spin susceptibility are also explained.

9 pages, 7 figures, references updated, to be published in PRL

References in corpus (15)

• Unconventional pairing originating from disconnected Fermi surfaces in superconducting LaFeAsO${}_{1-x}$F${}_x$}
• Near-degeneracy of several pairing channels in multiorbital models for the Fe-pnictides
• Magnetism, superconductivity, and pairing symmetry in Fe-based superconductors
• Strong Correlations and Magnetic Frustration in the High Tc Iron Pnictides
• Theory of Electron Nematic Order in LaOFeAs
• Ising and Spin orders in Iron-based Superconductors
• The quadrupolar phases of the S=1 bilinear-biquadratic Heisenberg model on the triangular lattice
• Iron pnictides as a new setting for quantum criticality
• Nature of magnetic excitations in superconducting BaFe${}_{1.9}$Ni${}_{0.1}$As${}_2$
• Persistent high-energy spin excitations in iron pnictide superconductors
• Interplay between magnetic properties and Fermi surface nesting in iron pnictides
• Pnictides as frustrated quantum antiferromagnet close to a quantum phase transition
• Spin-state transition in the Fe-pnictides
• Similar zone-center gaps in the low-energy spin-wave spectra of NaFeAs and BaFe2As2
• Theory of spin nematic to spin-Peierls quantum phase transition in ultracold spin-1 atoms in optical lattices

Cited by in corpus (24)

• Excitonic Magnetism in Van Vleck-type d^4 Mott Insulators
• Hidden symmetries of the extended Kitaev-Heisenberg model: Implications for honeycomb lattice iridates A2IrO3
• Crystallographic, Electronic, Thermal and Magnetic Properties of Single-Crystal SrCo2As2
• Excitonic Instability at the Spin-State Transition in the Two-Band Hubbard Model
• Phase diagram and collective excitation in excitonic insulator: from the orbital physics viewpoint
• Muon-spin-rotation study of the magnetic structure in the tetragonal antiferromagnetic state of weakly underdoped Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Progressive slowing down of spin fluctuations in underdoped LaFeAsO${}_{1-x}$F${}_x$
• Spin Ferroquadrupolar Order in the Nematic Phase of FeSe
• Crossover in the magnetic response of single-crystalline Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ and Lifshitz critical point evidenced by Hall effect measurements
• Structural origin of the anomalous temperature dependence of the local magnetic moments in the CaFe${}_2$As${}_2$ family of materials
• Soft striped magnetic fluctuations competing with superconductivity in Fe_{1+x}Te
• Doping Induced Spin State Transition in LaCoO3: Dynamical Mean-Field Study
• Hole-doping-induced melting of spin-state ordering in PrBaCo2O5.5+x
• Local and collective magnetism of EuFe${}_2$As${}_2$
• Highly frustrated magnetism in relativistic ${\mathbf{d}}^4$ Mott insulators: Bosonic analog of Kitaev honeycomb model
• Spin and quadrupolar orders in the spin-1 bilinear-biquadratic model for iron-based superconductors
• Muon spin rotation and infrared spectroscopy study of magnetism and superconductivity in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Orbital Symmetry and Orbital Excitations in High-$T_c$ Superconductors
• Nematicity in LaFeAsO${}_{1-x}$F${}_x$
• Excitonic ordering in strongly correlated spin crossover systems: induced magnetism and excitonic excitation spectrum
• Orbital altermagnetism on the kagome lattice and possible application to $A$V${}_3$Sb${}_5$
• Magnetotransport properties in the magnetic phase of BaFe${}_{2-x}$T${}_x$As${}_2$ (T = Co,Ni): A magnetic excitations approach
• Unified Spin Model for Magnetic Excitations in Iron Chalcogenides
• Strong local moment antiferromagnetic spin fluctuations in V-doped LiFeAs