Spin excitations in a model of FeSe with orbital ordering

Abstract

We present a theoretical study of the dynamical spin susceptibility for the intriguing Fe-based superconductor FeSe, based on a tight-binding model developed to account for the temperature-dependent band structure in this system. The model allows for orbital ordering in the $d_{xz}/d_{yz}$ channel below the structural transition and presents a strongly $C_4$ symmetry broken Fermi surface at low temperatures which accounts for the nematic properties of this material. The calculated spin excitations are peaked at wave vector $(\pi ,0)$ in the 1-Fe Brillouin zone, with a broad maximum at energies of order a few meV. In this range, the occurrence of superconductivity sharpens this peak in energy, creating a $(\pi ,0)$ "neutron resonance" as seen in recent experiments. With the exception of the quite low energy scale of these fluctuations, these results are roughly similar to standard behavior in Fe pnictide systems. At higher energies, however, intensity increases and shifts to wave vectors along the $(\pi ,0)$ - $(\pi ,\pi )$ line. We compare with existing inelastic neutron experiments and NMR data, and give predictions for further studies.

12 pages, 13 figures, published version, real-space hoppings for T=40 K included in source file

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• On the Remarkable Superconductivity of FeSe and its Close Cousins
• Orbital-dependent Fermi Surface shrinking as a fingerprint of nematicity in FeSe
• Anisotropic spin fluctuations in detwinned FeSe
• The Nematic Energy Scale and the Missing Electron Pocket in FeSe
• Electronic anisotropies revealed by detwinned ARPES measurements of FeSe
• Enhancement of Tc by point-like disorder and anisotropic gap in FeSe
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• Interplay of nematic and magnetic orders in FeSe under pressure
• Evidence for short-range magnetic order in the nematic phase of FeSe from anisotropic in-plane magnetostriction and susceptibility measurements
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• Effects of heavy-ion irradiation on FeSe
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• Non-local $d_{xy}$ nematicity and the missing electron pocket in FeSe
• Symmetry-unprotected nodes or gap minima in $s_{++}$ state of FeSe single crystal
• Theoretical study of impurity-induced magnetism in FeSe
• Role of multiorbital effects in the magnetic phase diagram of iron-pnictides
• Mechanism for nematic superconductivity in FeSe
• Spin triplet superconductivity driven by finite momentum spin fluctuations
• Interplay between superconductivity and itinerant magnetism in underdoped Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ ($x=$ 0.2) probed by the response to controlled point-like disorder
• Paramagnon dispersion in $\beta$-FeSe observed by Fe $L$-edge resonant inelastic x-ray scattering
• FeSe and the missing electron pocket problem
• Inter-orbital nematicity and the origin of a single electron Fermi pocket in FeSe
• Disorder-sensitive node-like small gap in FeSe
• Doping evolution of the normal state magnetic excitations in pressurized La3Ni2O7
• Theory of spin-excitation anisotropy in the nematic phase of FeSe obtained from RIXS measurements
• Nematic superconductivity from selective orbital pairing in Ba(Fe1-xMx)2As2 (M = Co, Ni) single crystals
• Magnetic excitations in the normal and nematic phases of iron pnictides
• Orbitally resolved superconductivity in real space: FeSe