Meissner type superconductivity extending up to 13 - 18 degrees Celsius was confirmed in the composite material consisting of metallic particles Ag5Pb2O6 dispersed in an insulating CuO matrix, and superconductivity mechanism is based upon inter particle interaction acting in the quantum tunnelling regime.
Quasi-two dimensional quantum magnetism is clearly highly correlated with superconducting ground states in cuprate-based High T$_c$ superconductivity. Three dimensional, commensurate long range magnetic order in La$_2$CuO$_4$ quickly evolves to quasi-two dimensional, incommensurate correlations on doping with mobile holes, and superconducting ground states follow for x as small as 0.05 in the La$_{2-x}$Sr$_x$/Ba$_x$CuO$_4$ family of superconductors. It has long been known that the onset of superconducting ground states in these systems is coincident with a remarkable rotation of the incommensu…
The dynamics of charge-ordered states is one of the key issues in underdoped cuprate high-temperature superconductors, but static short-range charge-order (CO) domains have been detected in almost all cuprates. We probe the dynamics across the CO (and structural) transition in La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_{4}$ by measuring nonequilibrium charge transport, or resistance $R$ as the system responds to a change in temperature and to an applied magnetic field. We find evidence for metastable states, collective behavior, and criticality. The collective dynamics in the critical regime indicat…
Critical Doping for the Onset of Fermi-Surface Reconstruction by Charge-Density-Wave Order in the Cuprate Superconductor La$ _{2-x} $Sr$_{x} $CuO$ _{4}$
Both Zn-doping and $c$-axis magnetic fields have been observed to increase the spin stripe order in La$_{2-x}$Ba$_x$CuO$_4$ with $x$ close to 1/8. For $x=0.095$, the applied magnetic field also causes superconducting layers to decouple, presumably by favoring pair-density-wave order that consequently frustrates interlayer Josephson coupling. Here we show that introducing 1% Zn also leads to an initial onset of two-dimensional (2D) superconductivity, followed by 3D superconductivity at lower temperatures, even in zero field. We infer that the Zn pins pair-density-wave order locally, establishin…
Charge-density-wave order takes over antiferromagnetism in Bi$_2$Sr$_{2-x}$La$_x$CuO$_{6}$ superconductors
当自旋序被破坏时，铜氧化物中出现超导性，而电荷的作用则鲜为人知。最近，电荷密度波（CDW）被发现低于超导圆顶在YBa $_2$ Cu $_3$ O $_y$当施加一个高磁场垂直于CuO $_2$平面，这被认为是产生初始CDW的涡核，成为重叠。在这里，通过$^{63}$ Cu-核磁共振，我们报告了在单层Bi $_2$ Sr $_{2-x}$ La $_x$ CuO $_6$中，由不在平面中产生涡核的面内场诱导的CDW的发现。起始温度$T_{\rm CDW}$接管反铁磁有序温度$T_{\rm N}$，超过临界掺杂水平，超导性开始出现，并与伪能隙温度$T^{*}$成比例。这些结果提供了重要的见解自旋序，CDW和赝能隙之间的关系，以及它们与高温超导性的联系。
The evolution of the structural and transport properties of underdoped La$_{1.952}$Sr$_{0.048}$CuO$_4$ thin films under compressive epitaxial strain has been studied. The films of different thicknesses $d$ (from 26 nm to 120 nm) were deposited using an insulating target. The onset of superconductivity in the films is observed at temperatures as high as 26 K, while small residual resistance persists at low temperatures, indicating that superconductivity is inhomogeneous. The resistance measured under perpendicular magnetic field saturates below about 0.65 K, suggesting a possible existence of n…
The discovery of a magnetic-field-induced charge-density-wave (CDW) order in the pseudogap state via nuclear magnetic resonance (NMR) studies has highlighted the importance of "charge" in the physics of high transition-temperature ($T_{\rm c}$) superconductivity in copper oxides (cuprates). Herein, after briefly reviewing the progress achieved in the last few years, we report new results of $^{63,65}$Cu-NMR measurements on the CDW order and its fluctuation in the single-layered cuprate Bi$_2$Sr$_{2-x}$La$_x$CuO$_{6+δ}$. The NMR spectrum under both in- and out-of-plane magnetic fields above $ H…
We have carried out new neutron spectroscopic measurements on single crystals of La$_{1.6-x}$Nd$_{0.4}$Sr$_x$CuO$_4$ from 0.12 to 0.26 using time-of-flight techniques. These measurements allow us to follow the evolution of parallel spin stripe fluctuations with energies less than 33 meV, from x=0.12 to 0.26. Samples at these hole-doping levels are known to display static (on the neutron scattering time scale) parallel spin stripes at low temperature, with onset temperatures and intensities which decrease rapidly with increasing x. Nonetheless, we report remarkably similar dynamic spectral weig…
The interpretation of how superconductivity disappears in cuprates at large hole doping has been controversial. To address this issue, we present an experimental study of single-crystal and thin film samples of La$_{2-x}$Sr$_x$CuO$_4$ (LSCO) with $x\ge0.25$. In particular, measurements of bulk susceptibility on LSCO crystals with $x=0.25$ indicate an onset of diamagnetism at $T_{c1}=38.5$ K, with a sharp transition to a phase with full bulk shielding at $T_{c2}=18$ K, independent of field direction. Strikingly, the in-plane resistivity only goes to zero at $T_{c2}$. Inelastic neutron scatterin…
Transport measurements provide important characterizations of the nature of stripe order in the cuprates. Initial studies of systems such as La(1.6-x)Nd(0.4)Sr(x)CuO(4) demonstrated the strong anisotropy between in-plane and c-axis resistivities, but also suggested that stripe order results in a tendency towards insulating behavior within the planes at low temperature. More recent work on La(2-x)Ba(x)CuO(4) with x=1/8 has revealed the occurrence of quasi-two-dimensional superconductivity that onsets with spin-stripe order. The suppression of three-dimensional superconductivity indicates a frus…
Revealing the high-energy electronic excitations underlying the onset of high-temperature superconductivity in cuprates
在强关联系统中，费米能（EF）处的电子性质与高能尺度处的电子性质交织在一起。高温超导（HTSC）领域的关键挑战之一是理解与Mott类激发（|E-E $_{F}$|>1 eV）参与冷凝物的形成。在这里，我们展示了多体高能量CuO 2激发在1.5和2 eV和HTSC的发病之间的相互作用。这是揭示了一种新的光泵超连续探测技术，它提供了访问的动态介电函数在Bi $_2$ Sr $_2$ Ca $_{0.92}$ Y $_{0.08}$ Cu $_2$ O $_{8+δ}$在一个扩展的能量范围内，光诱导抑制后的超导配对。这些结果揭示了一个非常规的机制在HTSC的基础上低于和高于最佳空穴浓度所需的达到最大临界温度（T $_c$）。
The rate of quasiparticle recombination probes the onset of coherence in cuprate superconductors
电子超流在临界温度$T_c$从常规金属态凝聚的过程可以用BCS理论很好地描述。在低掺杂的铜氧化物中，高温超导性反而从非常规的金属“赝隙”相凝聚而成，该相表现出各种非费米液体性质。最近，已经清楚的是，电荷密度波（CDW）相存在于赝能隙区域内，出现在刚好高于$T_c$的温度$T_{CDW}$处。$T_c$和$T_{CDW}$的近似重合，以及CDW和低于$T_c$的超导有序的共存和竞争，表明它们密切相关。在这里，我们表明，这种非常规的前体的超流的冷凝反映在偏离BSC理论的预测准粒子的重组率。利用超快时间分辨反射率法研究了欠掺杂HgBa $_{2}$ CuO $_{4+δ}$（Hg-1201）和YBa $_{2}$ Cu $_{3}$ O $_{6+x}$（YBCO）单晶中准粒子复合寿命$τ_{qp}$随温度和磁场的变化.我们发现，$τ_{qp}(T)$表现出局部最大值在一个小的温度窗口附近的$T_c$，这是突出的在欠掺杂的样品与共存的电荷顺序和消失的应用程序的一个小的磁场。我们解释这种不寻常的，非BCS的行为，假定$T_c$标志着从相位波动SC/CDW复合顺序以上的SC/CDW冷凝物以下的过渡。我们的研究结果表明，在欠掺杂铜氧化物超流体是相干混合粒子-粒子和粒子-空穴对的凝聚。
Thermodynamic evidence for nematic phase transition at the onset of pseudogap in YBa$_2$Cu$_3$O$_y$
在寻求理解铜酸盐超导性的过程中，一个中心问题是赝能隙态的性质和起源，赝能隙态包含异常的电子态，如费米弧、电荷密度波（CDW）和$d$波超导性。一个基本上重要的，但长期存在争议的问题是赝能隙态是否是一个独特的热力学相，其特征在于低于起始温度$T^*$的对称性破缺。电子向列性（四重（$C_4$）旋转对称性破缺）已成为赝能隙范围内的一个关键特征，但向列相变的存在与否及其与赝能隙的关系仍未得到解决。在这里，我们报告的热力学测量的磁矩在欠掺杂制度的斜方晶系YBa $_2$ Cu $_3$ O $_y$与一个领域旋转的CuO $_2$平面，这使我们能够量化磁各向异性异常高的精度。在进入赝能隙区后，在$T^*$处表现出明显的扭结后，磁化率的面内各向异性增加。我们的掺杂依赖性分析表明，这种各向异性被保存在低于$T^*$，即使在极限的正交性的影响被消除。此外，过量的面内各向异性数据显示出显着的缩放行为相对于$T/T^*$在宽的掺杂范围。这些结果提供了热力学证据表明，赝能隙开始与二阶相变相变，这是不同于CDW过渡，伴随着平移对称性破缺。这表明赝能隙相界附近的涨落与正常状态下的奇怪金属行为有潜在的联系，从中出现了高$T_c$超导性。
