Evidence for High Tc cuprate superconductivity is found in a region of the phase diagram where non-superconducting Fermi liquid metals are expected. Cu valences estimated independently from both x-ray absorption near-edge structure (XANES) and bond valence sum (BVS) measurements are > 2.3 for structures in the homologous series (Cu0.75Mo0.25)Sr2(Y,Ce)sCu2O5+2s+δ with s = 1, 2, 3, and 4. The s = 1 member, (Cu0.75Mo0.25)Sr2YCu2O7+δ, 0 \leq δ \leq 0.5, is structurally related to YBa2Cu3O7 in which 25% of the basal Cu cations [i.e. those in the chain layer] are replaced by Mo, and the Ba cations are replaced by Sr. After oxidation under high pressure the s = 1 member becomes superconducting with Tc = 88K. The Cu valence is estimated to be ~2.5, well beyond the ~2.3 value for which other High-Tc cuprates are considered to be overdoped Fermi liquids. The increase in valence is attributed to the additional 0.5 oxygen ions added per chain upon oxidation. The record short apical oxygen distance, at odds with current theory, suggests the possibility of a new pairing mechanism but further experiments are urgently needed to obtain more direct evidence. From the structural point of view the members with s \geq 2 are considered to be equivalent to single-layer cuprates. All have Tc ~ 56 K which is significantly higher than expected because they also have higher than expected Cu valences. The XANES-determined valences normalized to give values in the CuO2 layers are 2.24, 2.25, and 2.26 for s = 2, 3, and 4, while the BVS values determined for the valence in the CuO2 layer alone are 2.31-2.34 for the s = 2 and 3 members. No evidence for periodic ordering has been detected by electron diffraction and high resolution imaging studies. The possibility that the charge reservoir layers are able to screen long range coulomb interactions and thus enhance Tc is discussed.
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。
Dispersive spin excitations in highly overdoped cuprates revealed by resonant inelastic x-ray scattering
利用共振非弹性X射线散射（RIXS）在铜$L$吸收边，我们已经观察到强烈的，分散的自旋激发在高度过掺杂的Tl $_2$ Ba $_2$ CuO $_{6+δ}$（超导$T_c =6$ K），一种化合物，其正常状态的电荷传输和热力学性质已被广泛研究，并显示出典型的费米液体行为。补充RIXS实验上稍过掺杂的Tl $_2$ Ba $_2$ CuO $_{6+δ}$（$T_c =89$ K）和Y $_{1-x}$ Ca $_{x}$ Ba $_2$ Cu $_3$ O $_{6+δ}$化合物跨越广泛的掺杂水平表明，这些激发表现出的能量和能量积分光谱权重密切类似的反铁磁振子在未掺杂的铜酸盐。令人惊讶的共存费米液体的电荷激发和高能量的自旋激发，让人想起反铁磁绝缘体在高度过掺杂的化合物提出了挑战，目前的理论模型的铜酸盐。
Incommensurate Antiferromagnetic Order in the Fe-substituted Bi-2201 Cuprate in the Heavily Overdoped Regime
Sophia University（上智大学）；RIKEN Nishina Center（理化学研究所仁科中心）；Institute for Materials Research, Tohoku University（东北大学材料科学研究所）；ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory（STFC卢瑟福阿普顿实验室ISIS脉冲中子与μ子源）；Neutron Scattering Division, Oak Ridge National Laboratory（橡树岭国家实验室中子散射部）；Institute for Solid State Physics, The University of Tokyo（东京大学固体物理研究所）；Department of Natural Sciences, Tokyo Denki University（东京电机大学自然科学系）
Quasiparticle relaxation dynamics in cuprates and lifetimes of low-energy states: Femtosecond data from underdoped to overdoped YBCO and mercury compounds
Investigation of fermionic pairing on two- dimensional tight binding lattice under phonon and electronic mechanisms within a simple Fermi liquid like scenario and beyond- possible consequences for superconductivity in overdoped cuprates
Cu-spin Correlation in the Electron-overdoped High-Tc Cuprate Thin Films of La_2-x_Ce_x_CuO_4_ Probed by Low-energy Muons
Sophia University（上智大学）；PSI Center for Neutron and Muon Sciences（瑞士保罗谢尔研究所中子与μ子科学中心）；Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK-IMSS)（高能加速器研究机构材料结构科学研究所）
Persistence of vortexlike phase fluctuations in underdoped to heavily overdoped Bi-2201 cuprates
National High Magnetic Field Laboratory, Florida State University（美国国家高磁场实验室）；Western Kentucky University（西肯塔基大学）；Florida State University（佛罗里达州立大学）；Tohoku University（东北大学）
Correlation between the strength of low-temperature T-linear normal-state resistivity and $T_{\rm c}$ in overdoped electron-doped cuprate superconductors
本文在动能驱动超导框架内，揭示了过掺杂电子掺杂型铜氧化物超导体中由自旋激发同时介导的电子umklapp散射与电子配对，自然导致了低温T线性正常态电阻率强度与超导转变温度$T_{\ m c}$之间的内在关联。
Checkerboard-type Zhang-Rice States in Overdoped Cuprate Superconductors
Shanghai University（上海大学）；Anhui University（安徽大学）；Soochow University（苏州大学）；Southeast University（东南大学）；National University of Singapore（新加坡国立大学）；University of British Columbia（不列颠哥伦比亚大学）
Theoretical investigation of the feasibility of electronic mechanism for superconducting pairing in overdoped cuprates with Fermi liquid like and Marginal Fermi liquid- like descriptions for the normal phase
Three-Dimensional Fermi Surface of Overdoped La-Based Cuprates
用软X射线角分辨光电子能谱研究了过掺杂高温超导体La $_{2-x}$ Sr $_x$ CuO $_4$和La $_{1.8-x}$ Eu $_{0.2}$ Sr $_x$ CuO $_4$ .费米面的面内和面外分量通过改变光发射角和入射光子能量来映射。沿波节方向未观察到$k_z$色散，而识别出显著的波腹$k_z$色散。基于紧束缚参数化，我们讨论了范霍夫奇点附近的态密度的影响。我们的研究结果表明，在过掺杂La $_{2-x}$ Sr $_x$ CuO $_4$中发现的大的电子比热不能仅仅归因于van-Hove奇异性。因此，我们提出了量子临界诱导的一个崩溃的赝能隙相作为一个合理的解释所观察到的电子比热增强。
