Abstract
Identifying the symmetry of the wave function describing the Cooper pairs is pivotal in understanding the origin of high-temperature superconductivity in iron-based superconductors. Despite nearly a decade of intense investigation, the answer to this question remains elusive. Here, we use the muon spin rotation/relaxation () technique to investigate the underlying symmetry of the pairing state of the FeSe superconductor, the basic building block of all iron-chalcogenide superconductors. Contrary to earlier studies on powders and crystals, we show that while the superconducting gap is most probably anisotropic but nodeless along the crystallographic axis, it is nodal in the plane, as indicated by the linear increase of the superfluid density at low temperature. We further show that the superconducting properties of FeSe display a less pronounced anisotropy than expected.
- Received 26 April 2018
- Revised 12 September 2018
DOI:https://doi.org/10.1103/PhysRevB.98.180501
©2018 American Physical Society