2020/02/29 by Jose Rodriguez, J. P. Rodriguez · 9 citations
Materials Science · Physics and Astronomy · #Brillouin zone #Condensed matter physics #Inelastic neutron scattering #Inelastic scattering #Iron-based superconductors research #Physics #Physics of Superconductivity and Magnetism #Quantum mechanics #Quasiparticle #Rare-earth and actinide compounds #Scattering #Spin wave #Superconductivity #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.102.024521
published in Physical review. B./Physical review. B 102(2) (American Physical Society) · 41 pages, 8 figures
openalex created_date 2020/02/14 · openalex publication_date 2020/07/29 · arxiv created 2020/07/31 · arxiv updated 2020/08/03 · openalex updated_date 2026/08/05
Recent inelastic neutron scattering studies by B. Pan et al. [Nat. Commun. 8, 123 (2017)] find evidence for spin resonances in an iron selenide high-Tc superconductor that persist at energies above the quasiparticle gap. The momenta of such spin excitations form a diamond around the checkerboard wave vector, \mathbitQAF, that is associated with the square lattice of iron atoms that makes up the system. It has been suggested that the ``hollowed-out'' spin-excitation spectrum is due to hidden N'eel order. We study such a hidden spin density wave (hSDW) state that results from nested Fermi surfaces at the center and at the corner of the unfolded Brillouin zone. It emerges within mean-field theory from an extended Hubbard model over a square lattice of iron atoms that contain the minimal dxz and dyz orbitals. Opposing N'eel order exists over the isotropic d+=dxz+idyz and d\ensuremath-=dxz\ensuremath-idyz orbitals. The dynamical spin susceptibility of the hSDW is computed within the random phase approximation, at perfect nesting. Unobservable Goldstone modes that disperse acoustically are found at \mathbitQAF. A threshold is found in the spectrum of observable spin excitations that forms a ``floating ring'' at \mathbitQAF also. The ring threshold moves down in energy toward zero with increasing Hund's rule coupling, while it moves up in energy with increasing magnetic frustration. Comparison with the normal-state features of the spin-excitation spectrum shown by electron-doped iron selenide is made. Also, recent predictions of a Lifshitz transition from the nested Fermi surfaces to Fermi surface pockets at the corner of the folded Brillouin zone will be discussed.