Abstract
We report specific heat measurements of the heavy fermion superconductor in the vicinity of the superconducting critical field , with magnetic fields in the [110], [100], and [001] directions, and at temperatures down to 50 mK. The superconducting phase transition changes from second to first order for fields above 10 T for and . In the same range of magnetic fields, we observe a second specific heat anomaly within the superconducting state. We interpret this anomaly as a signature of a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) inhomogeneous superconducting state. We obtain similar results for , with the FFLO state occupying a smaller part of the phase diagram.
- Received 16 April 2003
DOI:https://doi.org/10.1103/PhysRevLett.91.187004
©2003 American Physical Society