Abstract
Unlike the parent phases of the iron-arsenide high- superconductors, undoped FeSe is not magnetically ordered and exhibits superconductivity with . Equally surprising is the fact that applied pressure dramatically enhances the modest to . We investigate the electronic properties of FeSe using NMR to search for the key to the superconducting mechanism. We demonstrate that the electronic properties of FeSe are very similar to those of electron-doped FeAs superconductors, and that antiferromagnetic spin fluctuations are strongly enhanced near . Furthermore, applied pressure enhances spin fluctuations. Our findings suggest a link between spin fluctuations and the superconducting mechanism in FeSe.
- Received 22 February 2009
DOI:https://doi.org/10.1103/PhysRevLett.102.177005
©2009 American Physical Society