Observation of Spin Susceptibility Enhancement in the Possible FFLO State in CeCoIn${}_5$

Abstract

We report ${}^{115}$In nuclear magnetic resonance (NMR) measurements of the heavy-fermion superconductor CeCoIn${}_5$ in the vicinity of the superconducting critical field $H_{c2}$ for a magnetic field applied perpendicular to the $\hat{c}$-axis. A possible inhomogeneous superconducting state, Fulde-Ferrel-Larkin-Ovchinnikov (FFLO), is stabilized in this part of the phase diagram. In 11 T applied magnetic field, we observe clear signatures of the two phase transitions: the higher temperature one to the homogeneous superconducting state and the lower temperature phase transition to a FFLO state. It is found that the spin susceptibility in the putative FFLO state is significantly enhanced as compared to the value in a homogeneous superconducting state. Implications of this finding for the nature of the low temperature phase are discussed.

to appear in Phys. Rev. Lett

References in corpus (2)

• Unpaired Electrons in the Heavy-Fermion Superconductor CeCoIn_{5}
• Phase Diagram and Spectroscopy of FFLO states of two-dimensional d-wave superconductors

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