Magnetic excitations in ferro-pnictide materials controlled by a quantum critical point into hidden order - Condensed Matter > SuperconductivityReport as inadecuate




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Abstract: The two-orbital J1-J2 model that describes a square lattice of frustratedspin-1 iron atoms is analyzed within the linear spin-wave approximation and byexact diagonalization over a 4x4 cluster. A quantum critical point QCP isidentified that separates hidden magnetic order at weak Hund-s rule couplingfrom 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 linearspin-wave spectrum shows strong low-energy excitations centered at thewavenumbers that correspond to cSDW order. These disperse anisotropically. Afit to the magnetic excitation spectrum of ferro-pnictide materials obtainedrecently by inelastic neutron scattering measurements notably accounts for theabsence of softening at the wavenumber that corresponds to Neel order.



Author: J. P. Rodriguez

Source: https://arxiv.org/







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