Abstract
We present a NMR study of the quasi-two-dimensional heavy-fermion superconductor believed to host a Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state. In the vicinity of the upper critical field and with a magnetic field applied parallel to the plane, the NMR spectrum exhibits a dramatic change below which well coincides with the position of reported anomalies in specific heat and ultrasound velocity. We argue that our results provide the first microscopic evidence for the occurrence of a spatially modulated superconducting order parameter expected in a FFLO state. The NMR spectrum also implies an anomalous electronic structure of vortex cores.
- Received 27 May 2004
DOI:https://doi.org/10.1103/PhysRevLett.94.047602
©2005 American Physical Society