CoO2 is the parent compound for the superconductor NaxCoO2\cdot1.3H2O and was widely believed to be a Mott insulator. We performed 59Co nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) studies on LixCoO2 (x = 0.35, 0.25, 0.12, and 0.0) to uncover the electronic state and spin correlations in this series of compounds which was recently obtained through electrochemical de-intercalation of Li from pristine LiCoO2. We find that although the antiferromagnetic spin correlations systematically increase with decreasing Li-content (x), the end member, CoO2 is a non-correlated metal that well satisfies the Korringa relation for a Fermi liquid. Thus, CoO2 is not simply located at the limit of x->0 for AxCoO2 (A = Li, Na) compounds. The disappearance of the electron correlations in CoO2 is due to the three dimensionality of the compound which is in contrast to the highly two dimensional structure of AxCoO2.
Charge Freezing in Zig-zag Chain Cuprates PrBa2Cu4O8 Observed by Cu Nuclear Quadrupole Resonance
本文报道了PrBa $_{2}$ Cu $_{4}$ O $_{8}$（一种具有近四分之一填充带的准一维导体）的链Cu位的核四极共振（NQR）研究.核自旋-晶格弛豫速率$1/T_{1}$在100 K附近出现一个明显的峰，这是由电场梯度（EFG）的涨落引起的.自旋回波衰减率$1/T_{2}$在50 K附近的不同温度下观察到类似的峰。这些结果和低温下NQR谱的加宽表明，电子或离子起源的缓慢电荷波动在低温下逐渐冻结。
Zeeman Perturbed $^{63}$Cu Nuclear Quadrupole Resonance Study of the Vortex State of YBa$_2$Cu$_3$O$_{7-δ}$
利用$^{63}$-Cu核四极共振（NQR）方法，研究了在低临界场$H_{c1}$附近，沿c轴96 mT的低磁场下，对偏高掺杂的高$T_c$超导体YBa $_2$ Cu $_3$ O $_{7-δ}$（$T_{c}\sim$ 92 K）的取向多晶样品的涡旋态.我们在$T_c$以下的Zeeman微扰$^{63}$ Cu NQR谱中观察到核自旋-晶格弛豫时间$^{63}T_1$的频率分布。1/$^{63}T_1$的特征行为，相对于温度和频率取最小值，表明反铁磁自旋涨落的多普勒频移准粒子能谱的内部和外部涡核的显着作用。
Variation in Superconducting Symmetry against Pressure on Noncentrosymmetric Superconductor Cd$_2$Re$_2$O$_7$ Revealed by $^{185/187}$Re Nuclear Quadrupole Resonance
利用$^{185/187}$ Re核四极共振（NQR）技术研究了非中心对称超导体Cd $_{2}$ Re $_{2}$ O $_{7}$在不同晶体结构下的超导性质.通过交流磁化率测量确定的超导转变温度$T_{\rm c}$的压力依赖性与以前的电阻率测量结果一致[T. C.小林$et al$ .，日本物理学会杂志80，023715（2011）.]。在2.2 GPa以下，在核自旋-晶格弛豫速率$1/T_{1}$中，在$T_{\rm c}$正下方观察到明显的相干峰，表明常规的$s$波超导性。与此相反，相干峰消失在3.1 GPa，这表明超导对称性的$p$波的优势状态对压力的变化。
Detection of an Unconventional Superconducting Phase in the Vicinity of the Strong First-Order Magnetic Transition in CrAs Using ^75As-Nuclear Quadrupole Resonance
Evolution of an Unconventional Superconducting State inside the Antiferromagnetic Phase of CeNiGe$_3$ under Pressure: a $^{73}$Ge-Nuclear-Quadrupole-Resonance Study
Antiferromagnetic Spin Fluctuation above the Superconducting Dome and the Full-Gaps Superconducting State in LaFeAsO1-xFx Revealed by 75As-Nuclear Quadrupole Resonance
Magnetic and superconducting properties on S-type single-crystal CeCu$_2$Si$_2$ probed by $^{63}$Cu nuclear magnetic resonance and nuclear quadrupole resonance
我们进行了$^{63}$ Cu核磁共振/核四极共振测量，以研究CeCu $_2$ Si $_2$的“超导主导”（$S$型）单晶的磁性和超导（SC）性质。虽然反铁磁（AFM）涨落的发展下降到1~K表明AFM临界性接近，但在0.8~K以下观察到Korringa行为，而在$T_{\rm c} \sim$ 0.6 K以上没有观察到磁异常。这些行为在$S$型CeCu $_2$ Si $_2$中是预期的。零场下的核自旋-晶格弛豫速率$1/T_1$的温度依赖性在130 mK以下与以前的多晶样品几乎相同，但在120 mK以下则向下偏离。事实上，SC态的$1/T_1$可以用双能隙$s_{\pm}$ -波模型来拟合，而不是用双能隙$s_{++}$ -波模型来拟合。在磁场下，在两个方向上的自旋磁化率明显降低到低于$T_{\rm c}$，表明形成了自旋单重态配对。自旋磁化率的剩余部分由$1/T_1T$计算的场致剩余态密度来理解，这归因于涡核的影响。在上临界场$H_{c2}$以上没有观察到磁异常，但观察到AFM涨落的发展，表明在强AFM涨落中实现了超导。
Cu Nuclear Quadrupole Resonance Study of La_{2-x}Sr_xCu_{1-y}Zn_yO_4 (x=0.10, 0.15 and 0.20): Zn-induced Wipeout Effect near the Magnetic and Electric Instability
Nematic transition and highly two-dimensional superconductivity in BaTi$_2$Bi$_2$O revealed by $^{209}$Bi-nuclear magnetic resonance/nuclear quadrupole resonance measurements
在这篇快速通讯中，一组$^{209}$ Bi-核磁共振（NMR）/核四极共振（NQR）测量已经完成，从微观角度研究超导（SC）BaTi $_2$ Bi $_2$ O的物理性质。5~K时的NMR和NQR谱可以用非零的面内各向异性参数$η$再现，表明在Bi位处的面内四重对称性破缺而没有任何磁序，即，“电子竞技”。在SC状态下，核自旋-晶格弛豫速率除以温度，$1/T_1T$，不改变，甚至低于$T_{\rm c}$，而一个明确的SC过渡与抗磁信号观察。这一观察结果可归因于BaTi $_2$ Bi $_2$ O中的强二维性。通过比较BaTi $_2$ $Pn$ $_2$ O（$Pn$ = As，Sb，Bi）的NMR/NQR结果，发现BaTi $_2$ Bi $_2$ O与BaTi $_2$ Sb $_2$ O和BaTi $_2$ As $_2$ O的正常和SC性质有很大的不同，这可能解释了该体系中$T_{\rm c}$的双圆顶结构.
Electron Paramagnetic Resonance Spectroscopy of Er$^{3+}$:Y$_2$SiO$_5$ Using Josephson Bifurcation Amplifier: Observation of Hyperfine and Quadrupole Structures
