Abstract
We use inelastic neutron scattering to study spin excitation anisotropy in mechanically detwinned with and 0.054. Both samples exhibit a tetragonal-to-orthorhombic structural transition at , a collinear static antiferromagnetic order at wave vector below the temperature , and superconductivity below (). In the high-temperature paramagnetic tetragonal phase (), spin excitations centered at and are gapless and have fourfold () rotational symmetry. On cooling to below but above , spin excitations become highly anisotropic, developing a gap at but still are gapless at . Upon entering into the superconducting state, a neutron spin resonance appears at with no magnetic scattering at . By comparing these results with those from angle-resolved photoemission spectroscopy experiments, we conclude that the anisotropic shift of the and bands in detwinned below is associated with the spin excitation anisotropy, and the superconductivity-induced resonance arises from the electron-hole Fermi surface nesting of quasiparticles with the orbital characters.
4 More- Received 27 July 2019
- Revised 14 September 2019
DOI:https://doi.org/10.1103/PhysRevB.100.134509
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