Anisotropic spin fluctuations in detwinned FeSe.

ABSTRACT: Superconductivity in FeSe emerges from a nematic phase that breaks four-fold rotational symmetry in the iron plane. This phase may arise from orbital ordering, spin fluctuations or hidden magnetic quadrupolar order. Here we use inelastic neutron scattering on a mosaic of single crystals of FeSe, detwinned by mounting on a BaFe₂As₂ substrate to demonstrate that spin excitations are most intense at the antiferromagnetic wave vectors Q_AF?=?(±1, 0) at low energies E?=?6-11?meV in the normal state. This two-fold (C₂) anisotropy is reduced at lower energies, 3-5?meV, indicating a gapped four-fold (C₄) mode. In the superconducting state, however, the strong nematic anisotropy is again reflected in the spin resonance (E?=?3.6?meV) at Q_AF with incommensurate scattering around 5-6?meV. Our results highlight the extreme electronic anisotropy of the nematic phase of FeSe and are consistent with a highly anisotropic superconducting gap driven by spin fluctuations.

SUBMITTER: Chen T 

PROVIDER: S-EPMC7895486 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature