Study of the FFLO State and the Anomalous Magnetic Order in CeCoIn5

为了更好地理解CeCoIn5中奇异的超导电性和磁性如何相互作用，我们测量了115In核磁共振，并证明了在平行场中HL相中出现了空间分布的正常准粒子区。顺磁磁化强度和低能准粒子能级密度的场演化可以用与FFLO二级相变形成节面有关的序参量来描述。核磁共振谱随外场与a轴夹角的变化表明，其磁结构由空间均匀结构转变为空间调制结构。随着角度的增加，奇异的FFLO相被抑制，并消失超过20度。我们的结果为FFLO态的形成提供了强有力的证据，它是通过二级相变以及静态磁序和FFLO态的共存而形成的。

To improve our understanding of how the exotic superconductivity and magnetism can interact in CeCoIn5, we measured 115In NMR and demonstrate the emergence of a spatially distributed normal quasiparticle region in the HL-phase in parallel field. The field evolution of the paramagnetic magnetization and low energy quasiparticle DOS can be described well by the order parameter associated with the nodal plane formation via the FFLO second order phase transition. The evolution of NMR spectra with respect to angle between external field and a-axis reveasl that the magnetic structure changes from the spatially-uniform to the spatially-modulated one. The exotic FFLO phase is suppressed with increasing the angle, and disappears for beyond 20 degree.Our results provide strong evidence for the formation of the FFLO state via the second order phase transition and coexistence ot the static magnetic order and FFLO state.