M. Saitoh

Texture in the Superconducting Order Parameter of CeCoIn~5 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.

Fulde-Ferrell-Larkin-Ovchinnikov State in a Perpendicular Field of Quasi-Two-Dimensional CeCoIn5

A Fulde-Ferrell-Larkin-Ovchinnkov (FFLO) state was previously reported in the quasi-2D heavy fermion CeCoIn5 when a magnetic field was applied parallel to the ab plane. Here, we conduct 115In NMR studies of this material in a perpendicular field, and provide strong evidence for FFLO in this case as well. Although the topology of the phase transition lines in the H-T phase diagram is identical for both configurations, there are several remarkable differences between them. Compared to H parallelab, the FFLO phase for H perpendicularab is confined in a much narrower region at the low-T-high-H corner in the H-T plane, and the critical field separating the FFLO and non-FFLO superconducting states almost ceases to have a temperature dependence. Moreover, directing H perpendicularab results in a notable change in the quasiparticle excitation spectrum within the planar node associated with the FFLO transition.

NMR Study of the Field‐Induced Quantum Critical Behavior in CeCoIn5

We report In and Co Knight shift results for the heavy fermion superconductor CeCoIn5 in the normal state up to 8.0 T with the magnetic field parallel to the [001] crystal axis. Upon increasing the field from 5.0 T, the Knight shifts of both the In(1) and the Co sites are gradually suppressed, being consistent with the emergence of a Landau Fermi Liquid state from a Non Fermi Liquid state. We discuss the field dependence of the quantum criticality of CeCoIn5.

Microscopic Evidence for the FFLO State in CeCoIn5 Probed by NMR

An anomalous temperature dependence of the NMR spectrum has seen found in the newly‐discovered high field and low temperature superconducting phase of CeCoIn5. The present NMR study provides direct microscopic evidence that the Fulde‐Ferrel‐Larkin‐Ovchinikov (FFLO) state is realized in the heavy fermion superconductor, CeCoIn5.

Texture in the Superconducting Order Parameter ofCeCoIn5Revealed 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.