Study of the FFLO state with Anomalous Vortices in CeCoIn5

CeCoIn5 中反常涡旋 FFLO 态的研究

• 批准号: 20340082
• 负责人: KUMAGAI Ken-ichi
• 金额: $ 10.07万
• 依托单位: Hokkaido University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2007
• 资助国家: 日本
• 起止时间: 2007 至 2011
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-20340082/
• 关键词: 強相関係; 強相関電子系; 超伝導; 核磁気共鳴; 磁気秩序; FFLO相; FFLO; CeCoIn_5

The quasi-two dimensional heavy fermion superconductor CeCoIn_5 continues to excite great interest, because it shows a number of fascinating superconducting properties. CeCoIn_5 is an extremely clean high-κ superconductor with d-wave symmetry. The superconductivity of CeCoIn_5 at high fields is destroyed by Pauli paramagnetic effect, as evidenced by the first-order phase transition at the upper critical field H_c2. Closely related to the Pauli limited superconductivity, this high-field and low-temperature phase (HL-phase) has been attributed to the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. The presence of the FFLO state in CeCoIn5 has been supported by several experiments. However, recent NMR and neutron data in parallel field demonstrated a long-range static magnetic order in the HL-phase. Remarkably this incommensurate spin-density wave order vanishes when the superconductivity dies at H_c2, indicating that the magnetism and the exotic superconductivity are closely intertwined.In this study, to improve our understanding of how the exotic superconductivity and magnetism can interact in CeCoIn_5, we measured NMR spectra on the three distinct In sites. ^<115>In NMR measurements 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 NMR spectra also reveal that the spatially uniform SDW coexists with the FFLO nodal planes. The exotic HL-phase is suppressed with increasing the angle of the direction of magnetic field with respect to the a-axis, and disappears beyond θ～20°.Our results provide strong evidence for the formation of the FFLO state via the second order phase transition, which coexists with the static magnetic order.

准二维重费米子超导体CeCoIn_5由于具有许多令人着迷的超导性质而一直引起人们的极大兴趣。CeCoIn_5是一种具有d波对称性的高κ超导体。CeCoIn_5在高场下的超导电性被泡利顺磁效应破坏，在上临界场H_c2处出现一级相变。与泡利极限超导密切相关，这种高场低温相（HL相）被归因于富尔德-费雷尔-拉金-奥夫钦尼科夫（FFLO）态。CeCoIn 5中FFLO态的存在已经得到了几个实验的支持。然而，最近的核磁共振和平行场中子数据表明，在HL相的长程静态磁序。值得注意的是，当超导性在H_c2处消失时，这种无公度的自旋密度波序消失了，这表明磁性和奇异的超导性是紧密交织在一起的。在这项研究中，为了提高我们对奇异的超导性和磁性如何在CeCoIn_5中相互作用的理解，我们测量了三个不同In位置的NMR谱。^<115>In NMR测量表明在平行场中HL相中出现了空间分布的正常准粒子区域。顺磁磁化强度和低能准粒子态密度的场演化可以很好地用与通过FFLO二级相变形成节面相关的序参量来描述。NMR谱还表明空间均匀的SDW与FFLO节面共存。随着磁场方向与a轴夹角的增大，奇异的HL相被抑制，当磁场方向与a轴夹角大于20°时，奇异的HL相消失.我们的结果为通过二级相变形成FFLO态提供了强有力的证据，这种二级相变与静态磁序共存.

项目成果

NMR study of magnetic and superconducting order of CeCoIn_5 in a high field and low temperature phase

CeCoIn_5高场低温相磁序和超导序的核磁共振研究

• 发表时间: 2009
• 作者: K. Kumagai;N. Kondoh;H. Shishido;and Y. Matsuda
• 通讯作者: and Y. Matsuda

NMR Study of a New Superconducting phase in a strongly-corre lated electron system of CeColn_5

CeColn_5强相关电子系统中新超导相的核磁共振研究

• 发表时间: 2008
• 作者: K. Kumagai;N. Kondoh;H. Shishido;and Y. Matsuda;K Kumagai;K.Kumagai;K.Kumagai;K.Kumagai;K. Kumagai;K. Kumagai
• 通讯作者: K. Kumagai

NMR Study of the FFLO State and Magnetism in CeCoIn5

CeCoIn5 中 FFLO 状态和磁性的核磁共振研究

• 发表时间: 2011
• 作者: K. Kumagai;H. Shishido;T. Shibauchi and Y. Matsuda
• 通讯作者: T. Shibauchi and Y. Matsuda

NMR Study of Magnetic Order and Spatially-Modulated Superconducting Gap in CeCoIn5

CeCoIn5 中磁序和空间调制超导能隙的核磁共振研究

• 发表时间: 2012
• 作者: K. Kumagai;H. Shishido;T. Shibauchi and Y. Matsuda
• 通讯作者: T. Shibauchi and Y. Matsuda

Field Evolution of the FFLO State and Magnetism in CeCoIn5

CeCoIn5 中 FFLO 状态和磁性的场演化

• 发表时间: 2011
• 作者: K. Kumagai;H. Shishido;T. Shibauchi and Y. Matsuda
• 通讯作者: T. Shibauchi and Y. Matsuda