为了解释在高$T_{\rm c}$超导体中观察到的高能扭折（HEK）的起源，我们对Nd $_{1.85}$ Ce $_{0.15}$ CuO $_{4}$（NCCO）进行了角分辨光电子能谱（ARPES）研究。与空穴掺杂的HTSC相比，NCCO中的HEK的能量尺度较大，与先前的ARPES研究一致。从测量在一个很宽的动量区域，我们已经证明，之间的空穴和电子掺杂的HTSC的HEK的能量位置被移动的化学电势差的量。在$(π, 0)$附近，HEK几乎与能带底部重合，而在波节附近，能带到达非相干区，HEK出现在相干区和非相干区的边界。
英文摘要：
We have performed an angle-resolved photoemission spectroscopy (ARPES) study of Nd$_{1.85}$Ce$_{0.15}$CuO$_{4}$ (NCCO) in order to elucidate the origin of the high-energy kink (HEK) observed in the high-$T_{\rm c}$ superconductors (HTSCs). The energy scale of the HEK in NCCO is large compared with that in hole-doped HTSCs, consistent with previous ARPES studies. From measurement in a wide momentum region, we have demonstrated that between the hole- and electron-doped HTSCs the energy position of the HEK is shifted approximately by the amount of the chemical potential difference. Also, we have found that around $(π, 0)$ the HEK nearly coincides with the band bottom while around the node the band reaches the incoherent region and the HEK appears at the boundary between the coherent and incoherent regions.
Angle-resolved photoemission spectroscopy (ARPES) measurements have established the phenomenon of kink in band dispersion of high-$T_{\rm c}$ cuprate superconductors. However, systematic studies of the kink in electron-doped cuprates are still lacking experimentally. We performed $in$-$situ$ ARPES measurements on ${\rm La}_{2-x}{\rm Ce}_x{\rm CuO}_{4\pmδ}$ (LCCO) thin films over a wide electron doping ($n$) range from 0.05 to 0.23. While the nodal kink is nearly invisible, an antinodal kink around 45 meV, surviving above 200 K, is observed for $n\sim0.05-0.19$, whose position is roughly indepe…
Identification of Nodal Kink in Electron-Doped (Nd$_{1.85}$Ce$_{0.15}$)CuO$_4$ Superconductor from Laser-Based Angle-Resolved Photoemission Spectroscopy
对电子掺杂的（Nd $_{1.85}$ Ce $_{0.15}$）CuO $_4$高温超导体进行了高分辨激光角分辨光电子能谱测量。我们揭示了一个明确的扭结在$\sim$ 60毫电子伏的色散沿（0，0）-（$π$，$π$）节方向，伴随着峰-谷-驼峰功能的光电子能谱。这表明，在电子掺杂的超导体中，节点电子与集体激发（玻色子）耦合，声子是最有可能的玻色子候选者。这一发现建立了一个普遍性的节点电子耦合在空穴和电子掺杂的高温铜氧化物超导体。
The renormalization of the electrons in cuprate superconductors is characterized by the kink in the quasiparticle dispersion. Here the bilayer coupling effect on the quasiparticle dispersion kink in the electron-doped bilayer cuprate superconductors is studied based on the kinetic-energy-driven superconductivity. It is shown that the kink in the quasiparticle dispersion is present all around the electron Fermi surface, as the quasiparticle dispersion kink in the single-layer case. However, in comparison with the corresponding single-layer case, the kink effect in the quasiparticle dispersion a…
Holographic superconductor model represents various inhomogeneous solutions with homogeneous sources. In this paper, we study inhomogeneous structures in the presence of the homogeneous current and the chemical potential. We find single complex kink condensates, multiple complex kinks condensates and twisted kink crystal condensates in which both the amplitude and the phase of the order parameter modulate in space. Analyzing the gauge-invariant phase difference in the single complex kink condensates, we find the non-monotonic behaviour with respect to the current. We confirm that the multiple …
In a conventional framework, superconductivity is lost at a critical temperature (T_c) because, at higher temperatures, gluing bosons can no longer bind two electrons into a Cooper pair. In high-T_c cuprates, it is still unknown how superconductivity vanishes at T_c. We provide evidence that the so-called <~70-meV kink bosons that dress the quasi-particle excitations are playing a key role in the loss of superconductivity in a cuprate. We irradiated a 170-fs laser pulse on Bi2Sr2CaCu2O8+δand monitored the responses of the superconducting gap and dressed quasi-particles by time- and angle-resol…
We investigated quantized modes of kinks in the phase space of superconducting gaps in a superconductor with multiple gaps. The kink is described by the sine-Gordon model in a two-gap superconductor and by the double sine-Gordon model in a three-gap superconductor. A fractional-flux vortex exists at the edge of the kink, and a fractional-flux vortex will be stable in a three-gap superconductor with time-reversal symmetry breaking. The kink and fractional-flux vortex exhibit massless modes as a sliding motion. We show further that there are one zero-energy mode (massless mode) and quantized exc…
Momentum-dependence of Superconducting Gap, strong-coupling dispersion Kink, and tightly bound Cooper pairs in the high-Tc (Sr,Ba)1-x(K,Na)xFe2As2 superconductors
Magnetic-force-microscope study of interlayer "kinks" in individual vortices in underdoped cuprate YBa$_2$Cu$_3$O$_{6+x}$ superconductor
我们使用磁力显微镜的图像和操纵个别涡线线程单晶YBa $_2$铜$_3$ O $_{6.4}$，层状超导体。我们发现，当我们拉动一个固定涡的顶部时，它可能不会平滑地倾斜。有时，我们观察到一个漩涡分裂成离散的片段，可以描述为短叠的煎饼漩涡，类似于Benkraouda和Clem提出的“扭结”结构。定量分析给出了钉扎力和堆叠之间的耦合的估计。我们的测量突出了分层超导体中煎饼涡旋堆叠的离散性。
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
High Tc superconductors show a rich variety of phases associated with their charge degrees of freedom. Valence charges can give rise to charge ordering or acoustic plasmons in these layered cuprate superconductors. While charge ordering has been observed for both hole- and electron-doped cuprates, acoustic plasmons have only been found in electron-doped materials. Here, we use resonant inelastic X-ray scattering (RIXS) to observe the presence of acoustic plasmons in two families of hole-doped cuprate superconductors [La2-xSrxCuO4 (LSCO) and Bi2Sr1.6La0.4CuO6+d (Bi2201)], crucially completing t…
Absence of nodes in the energy gap of the high-temperature electron-doped Pr1.85Ce0.15CuO4-y superconductor using thermal conductivity and specific heat measurements
The normal state of cuprate superconductors exhibits many exotic behaviors qualitatively different from the Fermi liquid, the foundation of condensed matter physics. Here we demonstrate that non-Fermi liquid behaviors emerge naturally from scattering against an emergent Bose liquid. Particularly, we find a finite zero-energy scattering rate at low-temperature limit that grows linearly with respect to temperature, against clean fermions' generic non-dissipative characteristics. Surprisingly, three other seemingly unrelated experimental observations are also produced, including the well-studied …
Electronic nematicity is often found in unconventional superconductors, suggesting its relevance for electronic pairing. In the strongly hole-doped iron-based superconductors, the symmetry channel and strength of the nematic fluctuations, as well as the possible presence of long-range nematic order, remain controversial. Here, we address these questions using transport measurements under elastic strain. By decomposing the strain response into the appropriate symmetry channels, we demonstrate the emergence of a giant in-plane symmetric contribution, associated with the growth of both strong ele…
Hydrogen (H)-doped LaFeAsO is a prototypical iron-based superconductor. However, its phase diagram extends beyond the standard framework, where a superconducting (SC) phase follows an antiferromagnetic (AF) phase upon carrier doping; instead, the SC phase is sandwiched between two AF phases appearing in lightly and heavily H-doped regimes. We performed nuclear magnetic resonance (NMR) measurements under pressure, focusing on the second AF phase in the heavily H-doped regime. The second AF phase is strongly suppressed when a pressure of 3.0 GPa is applied, and apparently shifts to a highly H-do…
The origin of a ubiquitous bosonic coupling feature in the photoemission spectra of high-Tc cuprates, an energy-momentum dispersion 'kink' observed at ~70 meV binding energy, remains a two-decade-old mystery. Understanding this phenomenon requires an accurate description of the coupling between the electron and some collective modes. We report here ab initio calculations based on GW perturbation theory and show that correlation-enhanced electron-phonon interaction in cuprates gives rise to the strong kinks, which not only explains quantitatively the observations but provides new understanding …
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。
For electron-doped cuprates, the strong suppression of antiferromagnetic spin correlation by efficient reduction annealing by the "protect-annealing" method leads to superconductivity not only with lower Ce concentrations but also with higher transition temperatures. To reveal the nature of this superconducting state, we have performed angle-resolved photoemission spectroscopy measurements of protect-annealed electron-doped superconductors Pr$_{1.3-x}$La$_{0.7}$Ce$_{x}$CuO$_{4}$ and directly investigated the superconducting gap. The gap was found to be consistent with $d$-wave symmetry, sugges…
We study how manifestations of strong electron-phonon interaction (EPI) depend on the carrier concentration by solving the two-dimensional Holstein model for the spin-polarized fermions using an approximation free bold-line diagrammatic Monte Carlo (BDMC) method. We show that the strong EPI, obviously present at very small Fermion concentration, is masked by the Fermi blockade effects and Migdal's theorem to the extent that it manifests itself as moderate one at large carriers densities. Suppression of strong EPI fingerprints is in agreement with experimental observations in doped high tempera…
