Low energy theory of the t-t'-t''-U Hubbard Model at half-filling: interaction strengths in cuprate superconductors and an effective spin-only description of La_2CuO_4
J. -Y. P. Delannoy, M. J. P. Gingras, P. C. W. Holdsworth, A. -M. S. Tremblay
Spin-only descriptions of the half-filled one-band Hubbard model are relevant for a wide range of Mott insulators. In addition to the usual Heisenberg exchange, many new types of interactions, including ring exchange, appear in the effective Hamiltonian in the intermediate coupling regime. In order to improve on the quantitative description of magnetic excitations in the insulating antiferromagnetic phase of copper-oxide (cuprate) materials, and to be consistent with band structure calculations and photoemission experiments on these systems, we include second and third neighbor hopping parameters, t' and t'', into the Hubbard Hamiltonian. A unitary transformation method is used to find systematically the effective Hamiltonian and any operator in the spin-only representation. The results include all closed, four hop electronic pathways in the canonical transformation. The method generates many ring exchange terms that play an important role in the comparison with experiments on La2CuO4. Performing a spin wave analysis, we calculate the magnon dispersion as a function of U,t,t' and t''. The four parameters are estimated by fitting the magnon dispersion to the experimental results of Coldea et al. [Phys. Rev. Lett. 86, 5377, {2001}] for La2CuO4. The ring exchange terms are found essential, in particular to determine the relative sign of t' and t'', with the values found in good agreement with independent theoretical and experimental estimates for other members of the cuprate family. The zero temperature sublattice magnetization is calculated using these parameters and also found to be in good agreement with the experimental value estimated by Lee et al. [Phys. Rev. B 60, 3643 (1999)]. We find a value of the interaction strength U~8t consistent with Mott insulating behavior.
Thermal conductivity and specific heat of the linear chain cuprate Sr$_{2}$CuO$_{3}$: Evidence for thermal transport via spinons
本文测量了自旋为1/2的海森堡链状铜氧化物Sr $_{2}$ CuO $_{3}$的低温比热和热导率。除了一个几乎各向同性的声子热输运，我们发现一个准一维的过剩沿链方向的热导率，最有可能与自旋激发（自旋）。自旋能流主要受缺陷和声子散射的限制。通过比热数据的分析，估算出链内磁交换$J/k_{B}$为2650 K.
Field induced antiferromagnetism and $^{17}$O Knight shift anomaly in La$_2$CuO$_4$
研究了铜酸盐弱铁磁体La $_2$ CuO $_4$顺磁态的场感生反铁磁效应。平面氧的$^{17}$ O Knight位移被证明是一个有效的工具来检查在外部磁场中的铜酸盐的Dzyaloshinsky-Moriya耦合的影响。场致反铁磁性和各向异性反铁磁性对$^{17}$ K的贡献解释了La $_2$ CuO $_4$中$^{17}$ O NMR中观察到的异常。反铁磁对$^{17}$ O Knight位移贡献的实验观察，可能是解决铜酸盐中Dzyaloshinsky矢量意义问题的唯一途径。
Variable range hopping theory for the nodal gap in strongly underdoped cuprate Bi$_2$Sr$_{2-x}$La$_x$CuO$_{6+δ}$
最近的角分辨光电子能谱（ARPES）实验对强欠掺杂Bi $_2$ Sr $_{2-x}$ La $_x$ CuO $_{6+δ}$铜氧化物在节方向上报道了一个不寻常的间隙。这些铜酸盐的运输实验发现变量范围跳跃行为观察。这些铜酸盐具有电子和空穴掺杂，这导致了这种铜酸盐类似于部分补偿半导体的提议。节点间隙对应于这种半导体中的Efros-Schklovskii（ES）间隙。我们计算的掺杂依赖性和温度依赖性的ES间隙模型，并找到支持Efros-Schklovskii模型。
Structural transitions in a doped lanthanum cuprate
139La NMR and relaxation measurements have been performed on La{1.8-x}Eu{0.2}Sr{x}CuO{4} (x = 0.13 and 0.2) single crystals. The temperature dependence of the 139La NMR spectra in all the structural phases (HTT -> LTO -> LTT) reveals the non-vanishing tilt angle of the CuO6 octahedra in the HTT phase, opposed to the case of La{2-x}Sr{x}CuO{4} where the tilt angle disappears immediately above the transition. Since 139La relaxation data provide evidence of the thermodynamic critical fluctuations associated with the structural phase transitions , HTT -> LTO and LTO -> LTT, we conclude that the st…
Doping dependence of 2-spinon excitations in the doped 1D cuprate Ba$_2$CuO$_{3+δ}$
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory（斯坦福材料能源科学研究所，SLAC国家加速器实验室）；Department of Applied Physics, Stanford University（斯坦福大学应用物理系）；Department of Physics, Southern University of Science and Technology（南方科技大学物理系）；Diamond Light Source（钻石光源）；National Synchrotron Light Source II, Brookhaven National Laboratory（美国布鲁克海文国家实验室第二代同步辐射光源）
Magnetic Breakdown in the electron-doped cuprate superconductor Nd$_{2-x}$Ce$_x$CuO$_4$: the reconstructed Fermi surface survives in the strongly overdoped regime
本文报道了电子过掺杂铜氧化物超导体Nd $_{2-x}$ Ce $_x$ CuO $_4$中的半经典角度相关磁电阻振荡（AMRO）和Shubnikov-de Haas效应。我们的数据提供了令人信服的证据磁击穿系统。这表明，一个重建的多连接费米表面持续存在，至少在强磁场，直到超导制度的最高掺杂水平。结果表明，在电子掺杂铜氧化物超导体中，平移对称破缺与超导配对之间存在着密切的联系。
Doping evolution of the electronic structure in the single-layer cuprates Bi$_2$Sr$_{2-x}$La$_x$CuO$_{6+δ}$: Comparison with other single-layer cuprates
我们已经进行了角分辨光电子能谱和芯层X射线光电子能谱研究的单层铜酸盐Bi $_2$ Sr $_{2-x}$ La $_x$ CuO $_{6+δ}$（Bi 2201），并揭示了掺杂的电子结构的演变从轻掺杂到最佳掺杂区域。我们已经观察到的色散准粒子带的形成，费米“弧”的费米面的演变和化学势的移动与空穴掺杂在其他铜酸盐。Bi 2201中的掺杂演变类似于Ca $_{2-x}$ Na $_{x}$ CuO $_{2}$ Cl $_2$（Na-CCOC）中的掺杂演变，其中已经观察到朝向母绝缘体的较低哈伯德带的快速化学势偏移，但是与La $_{2-x}$ Sr $_{x}$ CuO $_{4}$（LSCO）中的掺杂演变完全不同，其中化学势不偏移，而色散带和费米弧/表面已经在轻掺杂区中的费米能级周围形成。利用紧束缚拟合定量分析了费米面形状和能带色散，推导出的次近邻跳跃积分$t'$也证实了与Na-CCOC的相似性和与LSCO的不同.
Observation of vortices and hidden pseudogap from scanning tunneling spectroscopic studies of electron-doped cuprate superconductor $Sr_{0.9}La_{0.1}CuO_2$
Point contact spectroscopy of the electron-doped cuprate superconductor Pr{2-x}Ce{x}CuO4: The dependence of conductance-voltage spectra on cerium doping, barrier strength and magnetic field
$d$-wave superconducting gap observed in protect-annealed electron-doped cuprate superconductors Pr$_{1.3-x}$La$_{0.7}$Ce$_{x}$CuO$_{4}$
对于电子掺杂的铜氧化物，强抑制的反铁磁自旋相关有效的还原退火的“保护退火”的方法导致超导不仅具有较低的Ce浓度，但也具有较高的转变温度。为了揭示这种超导态的本质，我们对保护退火的电子掺杂超导体Pr $_{1.3-x}$ La $_{0.7}$ Ce $_{x}$ CuO $_{4}$进行了角分辨光电子能谱测量，并直接研究了超导能隙。发现该间隙与$d$波对称性一致，表明强电子相关性持续存在，因此反铁磁自旋波动仍然是介导保护退火的电子掺杂的铜氧化物中的铜配对的候选者。
Anisotropic microwave conductivity of cuprate superconductors in the presence of CuO chain induced impurities
在动能驱动的超导机制下，研究了邻位Ⅱ型$_2$的微波电导各向异性.邻位-Ⅱ $_2$ $_3$ O $_{6.50}$的特征在于填充和空$\hat{b}$轴CuO链的周期性交替。考虑CuO链诱导的扩展各向异性杂质散射，基于准粒子激发和散射过程的节块近似，再现了邻位Ⅱ型$_2$微波电导各向异性的主要特征，包括$\hat{a}$轴和$\hat{b}$轴微波电导的能量和温度依赖性的强度和线形.我们的研究结果也证实了$\hat{b}$轴CuO链诱导杂质是各向异性的主要来源。
Anisotropic dressing of charge-carriers in the electron-doped cuprate superconductor Sm(1.85)Ce(0.15)CuO(4) from angle-resolved photoemission measurements
"Spin-Flop" Transition and Anisotropic Magnetoresistance in Pr_{1.3-x}La_{0.7}Ce_{x}CuO_{4}: Unexpectedly Strong Spin-Charge Coupling in Electron-Doped Cuprates
Proximity-Induced Nodal Metal in an Extremely Underdoped CuO$_2$ Plane in Triple-Layer Cuprates
Hiroshima University（广岛大学）；Institute for Molecular Science（分子科学研究所）；Hirosaki University（弘前大学）；Kyoto Univ Adv Sci, Nagamori Inst Actuators（京都大学先进科学研究院长森致动器研究所）；Tohoku University（东北大学）；National Institute of Advanced Industrial Science and Technology（产业技术综合研究所）；Stanford University（斯坦福大学）；The University of Tokyo（东京大学）；SLAC National Accelerator Laboratory（SLAC国家加速器实验室）；University of California, Santa Barbara（加州大学圣塔芭芭拉分校）
Normal state specific heat in the cuprates La$_{2-x}$Sr$_x$CuO$_4$ and Bi$_{2+y}$Sr$_{2-x-y}$La$_x$CuO$_{6+δ}$ near the critical point of the pseudogap phase
在低温下（低至$0.5~{\rm K}$）测量了铜酸盐超导体La $_{2-x}$ Sr $_x$ CuO $_4$和Bi $_{2+y}$ Sr $_{2-x-y}$ La $_x$ CuO $_{6+δ}$的比热$C$，掺杂$p$接近于$p^\star$，即赝能隙相开始的临界掺杂。施加高达$35~{\rm T}$的磁场以抑制超导性，从而在低温下直接进入正常状态，并能够在$T \to 0$确定$C_e$，即电子对正常状态比热的贡献。在La $_{2-x}$ Sr $_x$ CuO $_4$中，$x=p = 0.22$、$0.24$和$0.25$、$C_e / T = 15-16~{\rm mJmol}^{-1}{\rm K}^{-2}$中，$T = 2~{\rm K}$的值是在较高掺杂（$p > 0.3$）和较低掺杂（$p < 0.15$）下测量的值的两倍。这证实了在$p^\star\simeq 0.19$处$C_e$的掺杂依赖性中存在宽峰，如先前报道的其中超导电性被Zn杂质破坏的样品。此外，在这三种掺杂下，我们发现$T \to 0$的对数增长，使得$C_e / T \sim {\rm B}\ln(T_0/T)$。$p$的峰值和$T$的对数依赖性是量子临界的两个典型热力学特征。在非常不同的铜酸盐Bi $_{2+y}$ Sr $_{2-x-y}$ La $_x$ CuO $_{6+…
Anomalously high quasiparticle thermal conductivity in the underdoped cuprate superconductor HgBa$_{2}$CuO$_{4+δ}$
Université de Sherbrooke（舍布鲁克大学）；CEA Saclay（法国原子能和替代能源委员会萨克莱中心）；CNRS UPR3228, Univ. Grenoble Alpes, Univ. Toulouse, INSA-T（法国国家科学研究中心、格勒诺布尔阿尔卑斯大学、图卢兹大学）；IRL Frontières Quantiques, Université de Sherbrooke–CNRS（量子前沿研究所，舍布鲁克大学-法国国家科学研究中心）；Canadian Institute for Advanced Research（加拿大高级研究院）
Evolution of Fermi surface and normal-state gap in chemically substituted cuprates Bi$_{2}$Sr$_{2-x}$Bi$_{x}$CuO$_{6+δ}$
我们对化学取代的铜酸盐Bi $_{2}$ Sr $_{2-x}$ Bi $_{x}$ CuO $_{6+δ}$进行了系统的角分辨光电子能谱研究。我们观察到费米表面积与Bi取代含量$x$线性收缩，反映了这种化学取代的电子掺杂性质。此外，谱线宽度随着$x$的增加而迅速加宽，并且在超导-绝缘边界处变得完全不相干。在轻欠掺杂区观察到的d波状正常态带隙逐渐演变成大的软带隙，这在激发能量和温度方面线性地抑制了波腹光谱权重。结合在相同样品上获得的体电阻率数据，我们建立了在非常欠掺杂制度的库仑隙行为的出现。我们的研究结果揭示了高$T_c$铜酸盐中离面化学取代的双重作用，即掺杂和无序，并阐明了强关联和无序导致的量子电子态的本质.
