Local orthorhombic lattice distortions in the paramagnetic tetragonal phase of superconducting NaFe<sub>1-x</sub>Ni<sub>x</sub>As.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 30087342.
- Also identified by DOI 10.1038/s41467-018-05529-2 and PMC identifier 6081486.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Understanding the interplay between nematicity, magnetism and superconductivity is pivotal for elucidating the physics of iron-based superconductors. Here we use neutron scattering to probe magnetic and nematic orders throughout the phase diagram of NaFe<sub>1-x</sub>Ni<sub>x</sub>As, finding that while both static antiferromagnetic and nematic orders compete with superconductivity, the onset temperatures for these two orders remain well separated approaching the putative quantum critical points. We uncover local orthorhombic distortions that persist well above the tetragonal-to-orthorhombic structural transition temperature T<sub>s</sub> in underdoped samples and extend well into the overdoped regime that exhibits neither magnetic nor structural phase transitions. These unexpected local orthorhombic distortions display Curie-Weiss temperature dependence and become suppressed below the superconducting transition temperature T<sub>c</sub>, suggesting that they result from the large nematic susceptibility near optimal superconductivity. Our results account for observations of rotational symmetry breaking above T<sub>s</sub>, and attest to the presence of significant nematic fluctuations near optimal superconductivity.