Abstract
We use neutron polarization analysis to study spin excitation anisotropy in the optimally isovalent-doped superconductor () ( K). Different from optimally hole- and electron-doped , where there is a clear spin excitation anisotropy in the paramagnetic tetragonal state well above , we find no spin excitation anisotropy for energies above 2 meV in the normal state of (). Upon entering the superconducting state, significant spin excitation anisotropy develops at the antiferromagnetic (AF) zone center , while the magnetic spectrum is isotropic at the zone boundary . By comparing the temperature, wave vector, and polarization dependence of the spin excitation anisotropy in () and hole-doped ( K), we conclude that such anisotropy arises from spin-orbit coupling and is associated with the nearby AF order and superconductivity.
- Received 6 April 2017
- Revised 14 October 2017
DOI:https://doi.org/10.1103/PhysRevB.96.180503
©2017 American Physical Society