Texture in the superconducting order parameter of CeCoIn5 revealed by nuclear magnetic resonance.
We present a 115In NMR study of the quasi-two-dimensional heavy-fermion superconductor CeCoIn5 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 ab plane, the NMR spectrum exhibits a dramatic change below T*(H) 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.
Kakuyanagi
K
K
Division of Physics, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
Saitoh
M
M
Kumagai
K
K
Takashima
S
S
Nohara
M
M
Takagi
H
H
Matsuda
Y
Y