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

为了更好地理解CeCoIn5中奇异的超导性和磁性是如何相互作用的，我们测量了115In核磁共振，并在平行场中证明了hl相中出现了一个空间分布的正态准粒子区域。顺磁磁化和低能准粒子DOS的场演化可以用与FFLO二阶相变形成节点面相关的序参量来描述。核磁共振波谱随外场与a轴夹角的变化表明，磁性结构由空间均匀型向空间调制型转变。外来FFLO相位随角度的增加而被抑制，超过20度后消失。我们的研究结果为FFLO态的形成提供了强有力的证据，证明了静态磁序和FFLO态是通过二阶相变形成的。

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.