我们提出了新的正常和超导态特性的铁砷化物超导体Ba $_{0.6}$ K $_{0.4}$ Fe $_2$作为$_2$（$T_c$ = 38 K）的$^{57}$铁NMR测量。在正常状态下，测量的奈特位移和核自旋-晶格弛豫速率$(1/T_1)$证明了波数（$q$）依赖的自旋涨落的发展，除了在$q$ = 0，这可能是由于嵌套在断开的费米面。在超导状态下，在$^{57}$ Fe-Knight位移中的自旋分量在低温下减小到几乎为零，证明自旋单重态超导状态。的$^{57}$ Fe- $1/T_1$的结果是完全一致的$s^\pm$波模型与多个完整的差距，无论是电子或空穴掺杂。
英文摘要：
We present $^{57}$Fe-NMR measurements of the novel normal and superconducting-state characteristics of the iron-arsenide superconductor Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ ($T_c$ = 38 K). In the normal state, the measured Knight shift and nuclear spin-lattice relaxation rate $(1/T_1)$ demonstrate the development of wave-number ($q$)-dependent spin fluctuations, except at $q$ = 0, which may originate from the nesting across the disconnected Fermi surfaces. In the superconducting state, the spin component in the $^{57}$Fe-Knight shift decreases to almost zero at low temperatures, evidencing a spin-singlet superconducting state. The $^{57}$Fe-$1/T_1$ results are totally consistent with a $s^\pm$-wave model with multiple full gaps, regardless of doping with either electrons or holes.
A number of recent experiments indicate that the iron-chalcogenide FeSe provides the long-sought possibility to study bulk superconductivity in the cross-over regime between the weakly coupled Bardeen--Cooper--Schrieffer (BCS) pairing and the strongly coupled Bose--Einstein condensation (BEC). We report on $^{77}$Se nuclear magnetic resonance experiments of FeSe, focused on the superconducting phase for strong magnetic fields applied along the $c$ axis, where a distinct state with large spin polarization was reported. We determine this high-field state as bulk superconducting with high spatial…
UTe$_2$ is a recently discovered promising candidate for a spin-triplet superconductor. In contrast to conventional spin-singlet superconductivity, spin-triplet superconductivity possesses spin and angular momentum degrees of freedom. To detect these degrees of freedom and obtain the solid evidence of spin-triplet superconductivity in UTe$_2$, we performed $^{125}$Te-NMR measurement. We previously reported that the shoulder signal appears in NMR spectra below the superconducting (SC) transition temperature $T_{\rm c}$ in $H \parallel b$, and that a slight decrease in the Knight shift along the…
Doping dependence of Normal-state Property in the Iron-based Oxypnictide Superconductors LaFeAsO1-y probed by 57Fe-NMR and 75As-NMR/NQR
本文报道了贫氧铁基氧氮族化合物超导体LaFeAsO_{1-y} $. A microscopic phase separation between superconducting domains and magnetic domains is shown to take place in the underdoped sample, indicating a local inhomogeneity in association with the density distribution of oxygen deficiencies. As a result, 1/T_1T in the normal state of the superconducting domain decreases significantly upon cooling at both the Fe and As sites regardless of the electron-doping level in LaFeAsO_{1-y}. On the basis of this result, we claim that $ 1/T_1 T $ is not always enhanced by antiferromagnetic fluctuations close to an antiferromagn…
High-$T_c$ Iron-phosphide Superconductivity Enhanced by Reemergent Antiferromagnetic Spin Fluctuations in (Sr$_4$Sc$_2$O$_6$)Fe$_2$(As$_{1-x}$P$_{x}$)$_2$ probed by NMR
本文报道了[SrPDMATHABMM ScPDMATHABMN O $_6$ ] FePDMATHABMN的系统NMR研究（As $_{1-x}$ P $_x$）$_2$，其中铁氮族元素的局部晶格参数（Fe $Pn$）层与LaFe系列的层相似（As $_{1-x'}$ P $_{x'}$）O，其表现出两个分离的反铁磁（AFM）有序相，$x'$ =0-0.2时的AFM 1和$x'$ =0.4-0.7时的AFM 2。结果表明，当$x$ =0时，母体AFM 1相在$x$ =0.3-0.4时消失，对应的磷族元素高度（$h_{pn}$）为1.3-1.32 μ m，这与LaFe（As $_{1-x'}$ P $_{x'}$）O和各种母体铁磷族元素化合物相似。相比之下，AFM 2秩序报道的LaFe（作为$_{0.4}$ P $_{0.6}$）O不出现在$x\sim$ 0.8，虽然局部晶格参数的Fe $Pn$层和微观电子状态是非常相似的。尽管没有{ \it静态} AFM 2阶，但在大约$x\sim$ 0.8处观察到重新出现的{ \it动态} AFM自旋波动，这可以归因于AFM 2相的不稳定性。我们建议这种重新增强的AFM自旋波动发挥了重要作用，提高$T_c$到17 K的$x$ =0.8-1。最后，我们从微观角度讨论了复杂磁基态的普遍性和多样性，包括AFM 1和AFM 2相起源的差异，以及它们与铁磷…
To investigate spin susceptibility in a superconducting (SC) state, we measured the $^{125}$Te-nuclear magnetic resonance (NMR) Knight shifts at magnetic fields ($H$) up to 6.5 T along the $b$ and $c$ axes of single-crystal UTe$_2$, a promising candidate for a spin-triplet superconductor. In the SC state, the Knight shifts along the $b$ and $c$ axes ($K_b$ and $K_c$, respectively) decreased slightly and the decrease in $K_b$ was almost constant up to 6.5 T. The reduction in $K_c$ decreased with increasing $H$, and $K_c$ was unchanged through the SC transition temperature at 5.5 T, excluding th…
$^{119}$Sn-NMR investigations on superconducting Ca$_3$Ir$_4$Sn$_{13}$: Evidence for multigap superconductivity
利用$^{119}$ Sn核磁共振实验研究了Ca $_3$ Ir $_4$ Sn $_{13}$的体超导电性. BCS超导的自旋-晶格弛豫速率（$1/T_1$）有两个经典特征，即$T_c$之下的Hebel-Slichter相干峰和超导相的指数衰减。$^{119}$ Sn Knight位移在低于$T_c$时的显著降低表明自旋单重态超导性。自旋晶格弛豫速率（$1/T_1$）的温度依赖性令人信服地描述了多间隙各向同性超导带隙。目前的核磁共振实验没有看到任何迹象，增强自旋波动的正常状态。
Inverse coherence effects in nuclear magnetic relaxation rates as a sign of topological superconductivity
我们揭示了三维多轨道拓扑超导性可以通过体测量来识别，即，核磁共振弛豫（NMR）速率的温度依赖性。在临界温度$T_{\rm c}$以下，拓扑状态下的NMR速率表现出反峰轮廓，这与常规的$s$波状态相反。这种反转相干效应来自于相对于轨道和自旋自由度的序参量的扭曲。我们对Cu $_{x}$ Bi $_{2}$ Se $_{3}$模型的自洽计算证明了逆相干效应表现为核磁共振速率的凹形温度依赖性。我们提出一个时间反演不变的轨道单重态自旋三重态拓扑超导性的特点是温度依赖的NMR速率。
No anomalous spin fluctuation in optimally doped and overdoped iron-based oxypnictide superconductors LaFeAsO$_{1-x}$F$_x$ probed by muon spin relaxation
在最佳掺杂和过掺杂超导体LaFeAsO $_{1-x}$ F $_x$中进行了零场和纵向场μ子自旋弛豫测量，以研究在较宽的温度和纵向场范围内的磁涨落.在μ子的时间窗（10 $^{-5}\sim$ 10 $^{-9}$ s）内，我们没有观察到磁涨落随温度变化的迹象.考虑到目前的结果和其他结果，即，通过中子散射观察到的自旋涨落、核磁共振和光电子能谱观察到的类赝能隙行为，表明不仅自旋涨落，而且费米表面具有几种不同轨道贡献的多带特征可能在LaFeAsO $_{1-x}$ F $_x$的超导配对机制中发挥重要作用。
Spin dynamics in HTSC cuprates: The singlet--correlated band (or t-J-V) model and its applications
迄今为止，铜氧化物超导态自旋磁化率的计算都是在弱耦合近似下进行的。然而，已知铜酸盐属于Mott-Hubbard掺杂材料，其中电子相关性是重要的。本文在考虑强关联的单重关联能带模型下，导出了铜氧化物超导态自旋磁化率的解析表达式。自旋磁化率的表达式进行评估，使用的跳跃参数的值适合于测量的费米面的材料YBa 2Cu 3 O 7和Bi 2Sr 2CaCu 2 O 8。我们表明，现有的实验数据，这是直接相关的自旋磁化率可以解释一致的一组模型参数为每种材料。这些实验包括由非弹性中子散射观察到的磁共振峰和超导状态下NMR自旋位移、自旋-自旋和自旋-晶格弛豫速率的温度依赖性。
Orbital-Selective Coexistence of Interlayer Spin-Singlet Formation and SDW Order with Anomalous Spin Reconfiguration in Bilayer Nickelate La$_{3}$Ni$_{2}$O$_{7}$ Revealed by $^{17}$O-NMR
The University of Osaka（大阪大学）；The University of Tokyo（东京大学）；National Institute for Materials Science (NIMS)（国立材料研究所）
Quasiparticle spin susceptibility in heavy-fermion superconductors : An NMR study compared with specific heat results
在Kramers双重态晶体电场（CEF）费米液体模型的基础上，根据电子比热（$γ_{el}$）、核磁共振奈特位移（$K$）和核磁共振弛豫速率（$1/T_1$）的实验结果，讨论了各种重费米子（HF）超导体的准粒子自旋磁化率（$χ^{qp}$）. $χ^{qp}_γ$由增强索末菲系数$γ_{el}$和$χ^{qp}_{T_1}$通过$χ^{qp}_{T_1}=(N_Aμ_B/A_{hf})K^{qp}_{T_1}$关系式由准粒子柯林加关系式$T_1T(K^{qp}_{T_1})^2=const.$计算得到，其中$A_{hf}$是超精细耦合常数，$N_A$是玻尔磁子数，$μ_B$是玻尔磁子。对于偶宇称（自旋单重态）超导体CeCu $_2$ Si $_2$，CeCoIn $_5$和UPd $_2$ Al $_3$，在低于超导转变温度（$T_c$）时，奈特位移$δK^{obs}$的分数减小是由于由$χ^{qp}_γ$和$χ^{qp}_{T_1}$一致估计的重准粒子自旋磁化率的减小。这一结果使我们得出结论，重准粒子形成自旋单态库珀对CeCu $_2$ Si $_2$，CeCoIn $_5$和UPd $_2$ Al $_3$。另一方面，在UPt $_3$和UNi $_2$ Al $_3$中没有观察到奈特位移的减少，然而，$χ^{qp}_γ$和$χ^{qp}_{T_1}$的估计值足够大，可以通过实…
Carrier doping in Pr_{1+x}Ba_{2-x}Cu_3O_7 studied by NMR
用Pr和链位Cu的核磁共振研究了非超导Pr $_{1+x}$ Ba $_{2-x}$ Cu $_3$ O $_7$单晶中$_2$ -面掺杂的载流子类型。固溶体体系中的不同光谱表明，富Pr晶体中的空穴局域在与化学计量比样品中的空穴相似的状态，即Febrishbacher和Rice提出的$4f^2-2pπ$杂化带中。相反，在有利于富Ba相的条件下制备的晶体的光谱表明CuO $_2$平面中的张-赖斯单线态中存在空穴。我们的研究结果强烈支持的模型，最近报道的超导电性Pr 123-晶体是由于在不均匀的样品中的富Ba区域。
Unconventional Superconductivity in the Novel Layered Superconductor Fe(Te-Se) Investigated by $^{125}$Te NMR on the Single Crystal
我们首次对新型层状超导体Fe $_{1.04}$ Te $_{0.67}$ Se $_{0.33}$的单晶进行了$^{125}$ Te NMR研究。$H // a$和$H // c$的Knight位移的自旋部分在超导态被抑制，表明自旋单重态超导性。在超导态，$1/T_{1}$表现出幂律行为（$\sim T^{3}$），没有任何相干峰。剩余态密度和$T^{3}$定律的观测表明了超导带隙中线节点的存在。在正常状态下，探测自旋涨落的\textbf{q} -总和的$1/T_{1}T$在低温下增强。我们的研究结果表明，超导电性在Fe $_{1+δ}$ Te $_{1-x}$ Se $_{x}$是稳定的反铁磁自旋涨落的增长，以及在FeSe。
