The c-axis optical response of the underdoped cuprates is qualitatively different from its in-plane counterpart. The features of the pseudogap show themselves more prominently in the c-axis than in-plane. We compute both the c-axis and in-plane optical conductivity using the Yang-Rice-Zhang model of the underdoped cuprates. This model combined with coherent interlayer tunnelling is enough to explain the qualitative differences between the in-plane and c-axis data. We show how pseudogap features manifest themselves in the infrared and microwave conductivity within this model.
The underdoped region of the cuprate's phase diagram displays many novel electronic phenomena both in the normal and the superconducting state. Many of these anomalous properties have found a natural explanation within the resonating valence bond spin liquid phenomenological model of Yang-Rice-Zhang (YRZ) which includes the rise of a pseudogap. This leads to Fermi surface reconstruction and profoundly changes the electronic structure. Here we extend previous work to consider the shift in critical temperature on $^{16}$O to $^{18}$O substitution, The isotope effect has been found experimentally…
Tetragonal CuO (T-CuO) has attracted attention because of its structure similar to that of the cuprates. It has been recently proposed as a compound whose study can give an end to the long debate about the proper microscopic modeling for cuprates. In this work, we rigorously derive an effective one-band generalized $t\!-\!J$ model for T-CuO, based on orthogonalized Zhang-Rice singlets, and make an estimative calculation of its parameters, based on previous \textit{ab initio} calculations. By means of the self-consistent Born approximation, we then evaluate the spectral function and the quasipa…
Doped Spin Ladder: Zhang-Rice Singlets or Rung-centred Holes?
我们建立了一个单掺杂自旋梯的电荷转移模型，该模型与Sr $_{3}$ Ca $_{11}$ Cu $_{24}$ O $_{41}$中耦合自旋梯的本征掺杂平面有关。假设存在的实验观察到的电荷秩序在系统中，我们解决了模型使用Hartree-Fock近似。我们的研究结果表明，与最近的X射线吸收测量结果一致，相对于其他配置的掺杂空穴的张-赖斯单态的深刻的稳定性。
Yamaji effect and quantum oscillation in Yang-Rice-Zhang model of underdoped cuprates
Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）；Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences（中国科学院大学理论科学研究所）
Superconductivity found in doped NdNiO$_2$ is puzzling as two local symmetries of doped NiO$_2$ layers compete, with presumably far-reaching implications for the involved mechanism: a cuprate-like regime with Zhang-Rice singlets {\cblue is replaced by local triplet states at realistic values of charge-transfer energy, which would suggest a rather different superconductivity scenario from high-$T_c$ cuprates}. We address this competition by investigating Ni$_4$O$_8$ clusters with periodic boundary conditions in the parameter range relevant for the superconducting nickelates. With increasing val…
Visualizing the Zhang-Rice singlet, molecular orbitals and pair formation in cuprate
Tsinghua University（清华大学）；Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；New Cornerstone Science Laboratory（新基石科学实验室）；Frontier Science Center for Quantum Information（量子信息前沿科学中心）；Hefei National Laboratory（合肥国家实验室）
Optical properties of the pseudogap state in underdoped cuprates
最近对深度掺杂不足的铜氧化物的光学测量表明，相干德鲁德响应在超导圆顶末端以下仍然存在。此外，没有观察到光学有效质量的大的增加，即使在低至1%的掺杂。我们表明，这种行为是一致的，由杨，赖斯和张提出的共振价键自旋液体模型。在这个模型中，在接近莫特绝缘态的过程中，光学电导率的整体降低不是由有效质量的增加引起的，而是由Gutzwiller因子引起的，该因子描述了由于相关性而导致的相干性降低，以及费米表面的收缩，这减少了可用的载流子的数量。我们还表明，在这个模型中，赝能隙不修改的低温，低频的行为，虽然电导率的幅度大大降低了Gutzwiller因子。类似地，微波电导率的温度依赖性的曲线在形状上基本上没有变化，但是Gutzwiller因子对于理解所观察到的邻位-I和邻位-II YBa $_2$ Cu $_3$ O $_y$之间的幅度差异是必不可少的。
Recent experiments have revealed incommensurate charge density wave (CDW) in the pseudogap regime in underdoped cuprates, e.g. YBa$_2$Cu$_3$O$_{6+δ}$ and HgBa$_2$CuO$_{4+δ}$. However, its relationship with the pseudogap is still controversial. In this work, we take a phenomenological synthesis of the doped resonating valence bond (RVB) state and the CDW order. Starting from the Yang-Rice-Zhang Green's function ansatz for the doped RVB state [Phys. Rev. B {\bf 73}, 174501 (2006)], in which the Fermi surface is partially truncated into four nodal hole-like Fermi pockets by the antinodal RVB gap,…
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。
We apply the recent wavepacket formalism developed by Ossadnik to describe the origin of the short range ordered pseudogap state as the hole doping is lowered through a critical density in cuprates. We argue that the energy gain that drives this precursor state to Mott localization, follows from maximizing umklapp scattering near the Fermi energy. To this end we show how energy gaps driven by umklapp scattering can open on an appropriately chosen surface, as proposed earlier by Yang, Rice and Zhang. The key feature is that the pairing instability includes umklapp scattering, leading to an ener…
Unusual electronic ground state of a prototype cuprate: band splitting of single CuO_2-plane Bi_2 Sr_(2-x) La_x CuO_(6+delta)
通过极化的原位改变，对于最佳掺杂的（x=0.4）Bi $_{2}$ Sr $_{2-x}$ La $_{x}$ CuO $_{6+δ}$，在（pi，0）点处解决了费米能级附近的Zhang-Rice单重态带的小分裂（R.Manzke等人，PRB 63，R100504（2001）。在这里，我们治疗的动量依赖性和线型的分裂带的光电发射的EDC模式具有非常高的角度和能量分辨率。在主对称线$Γ$ M的很大一部分上也可以观察到分裂成两个目标发射，给出了各个贡献的色散。由于双层效应不可能存在于这种单层材料中，因此必须在从当前理论模型导出的单粒子去除谱函数的上下文中讨论结果。最突出的是微观相分离，包括条纹相形成，共存的反铁磁和无公度电荷密度波临界波动耦合到电子（热点），甚至自旋电荷分离内的Luttinger液体图片，所有导致非费米液体的行为在正常状态下，并具有严重的后果的方式超导状态的形式。特别讨论了观察自旋子和holon激发的可能性。
Hard X-ray Cu $2p$ Core-Level Photoemission of High-$T_c$ Cuprate Superconductors
用硬X射线光电子能谱（HX-PES）对单层La $_{2-x}$ Sr $_{x}$ CuO $_{4}$、La掺杂Bi $_2$ Sr $_{1.6}$ La $_{0.4}$ CuO $_{6+δ}$（Bi 2201）和双层Bi $_2$ Sr $_{2}$ CaCu $_{2}$ O $_{8+δ}$（Bi 2212）高温超导体中Cu $2p$芯能级谱进行了详细的研究.我们鉴定了Cu $^{2+}$衍生的（i）Zhang-Rice单线态（ZRS）特征，（ii）$d^{n+1}\underline{L}$（配体屏蔽）特征，（iii）$d^{n}$卫星特征，以及主峰中空穴掺杂衍生的高结合能特征。在Bi基铜酸盐中，与La $_{2-x}$ Sr $_{x}$ CuO $_{4}$相比，$d^{n}$卫星特征的强度似乎强烈增强。从X射线光子能量相关的测量，它表明，在卫星区域的强度增加与Bi $4s$核心水平的光谱强度。修正后的$d^{n}$卫星强度与Cu-O层的掺杂含量或层数无关。我们的研究结果表明，相关的ZRS功能和空穴掺杂引起的高结合能谱的主峰与超导电性的变化的相对强度。
