Magnetic excitations in ferro-pnictide materials controlled by a quantum critical point into hidden order

Abstract

The two-orbital J1-J2 model that describes a square lattice of frustrated spin-1 iron atoms is analyzed within the linear spin-wave approximation and by exact diagonalization over a 4x4 cluster. A quantum critical point (QCP) is identified that separates hidden magnetic order at weak Hund's rule coupling from a commensurate spins density wave (cSDW) at strong Hund's rule coupling. Although the moment for cSDW order is small at the QCP, the critical linear spin-wave spectrum shows strong low-energy excitations centered at the wavenumbers that correspond to cSDW order. These disperse anisotropically. A fit to the magnetic excitation spectrum of ferro-pnictide materials obtained recently by inelastic neutron scattering measurements notably accounts for the absence of softening at the wavenumber that corresponds to Neel order.

20 pages, 8 figures, added discussion on doping, published version

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Cited by in corpus (11)

• Hidden Magnetic Order in Triangular-Lattice Magnet Li2MnTeO6
• Emergent Nesting of the Fermi Surface from Local-Moment Description of Iron-Pnictide High-Tc Superconductors
• Superconductivity by Hidden Spin Fluctuations in Electron-Doped Iron Selenide
• Fermi surface pockets in electron-doped iron superconductor by Lifshitz transition
• Spin Resonances in Iron-Selenide High-Tc Superconductors by Proximity to Hidden Spin Density Wave
• Isotropic Cooper Pairs with Emergent Sign Changes in Single-Layer Iron Superconductor
• Fermi surfaces of iron-pnictide high-Tc superconductors from the limit of local magnetic moments
• Collective Mode at Lifshitz Transition in Iron-Pnictide Superconductors
• Particle-Hole Transformation in Strongly-Doped Iron-Based Superconductors
• Two-orbital quantum spin model of magnetism in the iron pnictides
• Quantum-Critical Spin-Density Waves in Iron-Selenide High-Tc Superconductors