Evidence for the Presence of the Fulde-Ferrell-Larkin-Ovchinnikov State in CeCu2Si2 Revealed Using 63Cu NMR
Evidence for the Presence of the Fulde-Ferrell-Larkin-Ovchinnikov State in CeCu2Si2 Revealed Using 63Cu NMR
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DOI：
10.1103/physrevlett.121.157004
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发表时间：
2018-10-12
影响因子：
8.6
通讯作者：
Steglich, F.
中科院分区：
文献类型：
--
作者：
Kitagawa, Shunsaku;Nakamine, Genki;Steglich, F.
为了研究CeCu_2Si_2在对破缺场附近的超导特性，在上临界磁场为μ H ~（-0）（c_2）附近对CeCu_2Si_2进行了核磁共振测量.在较低的磁场中，奈特位移和核自旋-晶格弛豫速率除以温度1/T1 T突然降低到SC转变温度Tc（H）以下，这是在传统自旋单重态超导性框架内理解的现象。相比之下，当平行或垂直于c轴施加接近μ H-0（c2）（0）的磁场时，1/T1 T在T-c（H）以下增强，并表现出广泛的最大值;尽管Knight位移在T-c（H）以下下降。最近在有机超导体kappa-（BEDT-TTF）（2）Cu（NCS）（2）中观察到的这种1/T1 T的增强表明在非均匀SC区域中存在高密度Andreev束缚态，这是Fulde-Ferrell-Larkin-Ovchinnikov相的标志。
Nuclear magnetic resonance measurements were performed on CeCu2Si2 in the presence of a magnetic field close to the upper critical field is mu H-0(c2) in order to investigate its superconducting (SC) properties near pair-breaking fields. In lower fields, the Knight shift and nuclear spin-lattice relaxation rate divided by temperature 1/T1T abruptly decreased below the SC transition temperature T-c(H), a phenomenon understood within the framework of conventional spin-singlet superconductivity. In contrast, 1/T1T was enhanced just below T-c(H) and exhibited a broad maximum when magnetic fields close to mu H-0(c2)(0) were applied parallel or perpendicular to the c axis; although the Knight shift decreased just below T-c(H). This enhancement of 1/T1T, which was recently observed in the organic superconductor kappa-(BEDT-TTF)(2) Cu(NCS)(2), suggests the presence of high-density Andreev bound states in the inhomogeneous SC region, a hallmark of the Fulde-Ferrell-Larkin-Ovchinnikov phase.