First principles investigations of the high temperature superconducting system Ba$_2$CuO$_{3+δ}$, recently discovered at $δ\approx0.2$ at $T_c=70$ K, are applied to demonstrate the effects of oxygen ordering on the electronic and magnetic properties. The observed `highly over-doped' superconducting phase displays stretched Cu-planar oxygen O$_{\rm P}$ distances and anomalously shortened Cu-apical O$_{\rm A}$ separations compared with other cuprates. The stoichiometric system $δ=0$, with its strongly one-dimensional (1D) Cu-O$_{\rm P}$ chain structure, when nonmagnetic shows 1D Fermi surfaces that lead, within density functional theory, to antiferromagnetic Cu-O$_{\rm P}$ chains (a spin-Peierls instability). Accounting for 1D fluctuations and small interchain coupling according to the theory of Schulz indicates this system, like Sr$_2$CuO$_3$, is near the 1D Luttinger-liquid quantum critical phase. The unusual Cu-O bond lengths per se have limited effects on other properties for $δ$=0. We find that a `doubled bilayer' structure of alternating Cu-O$_{\rm P}$ chains and wide rung Cu$_3$O$_4$ ladders is the energetically preferred one of three possibilities where the additional oxygen ions bridge Cu-O$_{\rm P}$ chains in the superconducting phase $δ=1/4$. Nominal formal valences of the three Cu sites are discussed. The six-fold (octahedral) site is the most highly oxidized, accepting somewhat more holes in the $d_{z^2}$ orbital than in the $d_{x^2-y^2}$ orbital. The implication is that two-band physics is involved in the pairing mechanism and the superconducting carriers. The Fermi surfaces of this metallic bilayer structure show both 1D and 2D strong (incipient) nesting instabilities, possibly accounting for the lack of clean single-phase samples based on this structure and suggesting importance for the pairing mechanism.
Intrinsic Hall response of the CuO2 planes in a chain-plane-composite system of YBa2Cu3Oy
测量了YBa $_2$ Cu $_3$ O $_y$非孪晶单晶在宽掺杂范围内的霍尔系数。我们表明，霍尔电导率和霍尔角的{ \it CuO $_2$平面}在YBa $_2$ Cu $_3$ O $_y$可以从可测量的输运性质提取，而不管导电的Cu-O链，也不是在平面各向异性的CuO $_2$平面。本分析使我们能够讨论真正的霍尔效应在CuO $_2$平面单独在YBa $_2$ Cu $_3$ O $_y$没有任何并发症，由于Cu-O链。
Unusual Fermi surface nesting in parent compounds of iron arsenic high temperature superconductors revealed by Angle Resolved Photoemission Spectroscopy
利用扫描隧道显微镜（STM）研究了高温超导体$_2$ O $_2$的解理面，发现一维CuO链中存在电荷密度波（CDW）调制.在同一时间，没有签名的CDW已被报道的光谱功能的链带先前研究的光电发射。我们使用软X射线角分辨光电子能谱（SX-ARPES）来检测在以前的工作中没有检测到的链衍生的表面带。发现新表面带的$2k_\textup{F}$为0.55 π，ε $^{-1}$，这与STM在直接空间中观察到的CDW波矢量相匹配。这揭示了费米面嵌套的相关性的CuO链中的CDW的形成在YBa $_2$ Cu $_2$ O $_{7-δ}$。与CDW顺序的短程性质的协议，新检测到的表面带表现出赝能隙，其能量尺度也对应于STM观察到的。
Magnetization and transport properties in the superconducting Pr$_{2}$Ba$_{4}$Cu$_{7}$O$_{15-δ}$ with metallic double-chain
我们报道了压力对由溶胶-凝胶技术合成的名义组成Pr $_{2}$ Ba $_{4}$ Cu $_{7}$ O $_{15-δ}$的磁化强度和输运性质的影响。在真空中对烧结态样品进行还原处理，导致更高的超导性，实现了$δ=0.94$的$T_{c,on}=\sim 30$ K。在氧耗尽的样品上应用流体静压将其起始温度提高到36 K，在1.2 GPa下，表明与具有$δ=0.45$的较低$T_{c}$样品的压力依赖性相比，电荷载流子的几乎最佳掺杂水平。超导样品的Seebeck系数在低于$T_{c,on}$时出现明显的下降，在低于100 K时与非超导样品的Seebeck系数有很大的不同。这一发现有力地表明，由于还原处理的超导电性的外观沿CuO双链的电子状态的急剧变化。
Why phase diagrams of different underdoped cuprates are remarkably different? Disorder versus bilayer
与广泛接受的观点相反，La $_{2-x}$ Sr $_x$ CuO $_4$和YBa $_2$ Cu $_3$ O $\rm_{6+y}$的相图尽管相似，但却明显不同。导电性质和公度/非公度自旋有序性质都有很大的不同。有人认为，在YBCO的作用是微不足道的，而双层结构是至关重要的。另一方面，在LSCO中，内在无序在很大程度上驱动系统的性质。所开发的方法解释了系统的低温磁性。最重要的一点是关于无公度自旋排序的差异，包括无公度螺距的差异。分析表明，超导性与无公度自旋有序密切相关。
