Despite over two decades of intense research efforts, the origin of high-temperature superconductivity in the copper oxides remains elusive. Angle-resolved photoemission experiments (ARPES) revealed a kink in the dispersion relations (energy vs. wavevector) of electronic states in the cuprates at binding energies of 50-80 meV, and raised the hope that this anomaly could be key to understanding high-temperature superconductivity. The kink is often interpreted in terms of interactions between the electrons and a bosonic field. While there is no consensus on the nature of the bosons or even whether a boson model is appropriate, phonons and spin fluctuations have alternatively been proposed as possible candidates. Here we report state-of-the-art first-principles calculations of the role of phonons and the electron-phonon interaction in the photoemission spectra of La2-xSrxCuO4 (LSCO). Our study demonstrates that the phonon-induced renormalization of the electron energies and the Fermi velocity is almost one order of magnitude smaller than the effect observed in photoemission experiments. Hence, the present finding rules out electron-phonon interaction in bulk LSCO as the possible origin of the measured kink. This result should bear on several proposed theories of high temperature superconductivity in addition to theories concerning the origin of kinks in cuprate photoemission data.
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…
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 …
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。
We consider photoemission from cuprate high-temperature superconductors taking into account joint relaxation of strongly coupled fields: a field of correlated electrons and phonon field. Such relaxation occurs in systems with predominantly long-range electron-phonon interaction at sufficiently high carrier concentration due to coexistence of autolocalized and delocalized carriers. A simple method to calculate analytically a high-energy part of the ARPES spectrum arising is proposed. The approach suggested yields all the high-energy spectral features like broad bands of Gaussian shape and verti…
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 …
We investigate the electronic dispersion of the high-T$_{\mathrm{c}}$ cuprate superconductors using the fully self-consistent version of the phenomenological model, where charge planar quasiparticles are coupled to spin fluctuations. The inputs we use ---the underlying (bare) band structure and the spin susceptibility $χ$--- are extracted from fits of angle resolved photoemission and inelastic neutron scattering data of underdoped YBa$_{2}$Cu$_{3}$O$_{6.6}$ by T. Dahm and coworkers (T. Dahm et al., Nat. Phys. 5, 217 (2009)). Our main results are: (i) We have confirmed the finding by T. Dahm an…
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。
We employ Momentum-Resolved Electron Energy Loss Spectroscopy (M-EELS) on Bi2.1Sr1.9CaCu2O8+x to resolve the issue of the kink feature in the electron dispersion widely observed in the cuprates. To this end, we utilize the GW approximation to relate the density response function measured in in M-EELS to the self-energy, isolating contributions from phonons, electrons, and the momentum dependence of the effective interaction to the decay rates. The phononic contributions, present in the M-EELS spectra due to electron-phonon coupling, lead to kink features in the corresponding single-particle sp…
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…
In the course of seeking the microscopic mechanism of superconductivity in cuprate high temperature superconductors, the pseudogap phase\textemdash the very abnormal 'normal' state on the hole-doped side\textemdash has proven to be as big of a quandary as superconductivity itself. Angle-resolved photoemission spectroscopy (ARPES) is a powerful tool for assessing the momentum-dependent phenomenology of the pseudogap, and recent technological developments have permitted a more detailed understanding. This report reviews recent progress in understanding the relationship between superconductivity …
Temperature dependence of the angle resolved photoemission spectra in the undoped cuprates: self-consistent approach to the t-J-Holstein model
我们开发了一种新的自洽方法来研究角分辨光电子能谱（ARPES）的一个洞的t-J-Holstein模型给出完美的协议与数字精确的Diagrammatic Monte Carlo数据在零温度下的所有制度的电子-声子耦合。推广到有限温度的方法，我们发现，在未掺杂的铜酸盐的ARPES的异常温度依赖性的解释合作的相互作用的耦合的孔的磁波动和强的电子-声子相互作用。
Evidence for forward scattering and coupling to acoustic phonon modes in high-T$_c$ cuprate superconductors
最近的激光角分辨光电子能谱研究已经建立了一个新的扭结的存在下，在低能量节分散的Bi $_2$ Sr $_2$ CaCu $_2$ O $+{8+δ}$（Bi-2212）。这种扭结的能量尺度（~8-15 meV）出现在超导能隙$δ_0$的最大值以下。因此，很难解释这个特点，在通常的耦合到一个尖锐的色散模式。在本文中，我们研究了电子-声子耦合的面内声学声子支所产生的屏蔽库仑势的调制。我们证明，这种耦合具有较强的前向散射峰，因此，在能量尺度被局部间隙$δ(k)$移动的情况下，色散中发生扭结。此外，考虑减少屏蔽与欠掺杂自然解释了所观察到的低能量扭结的掺杂依赖性。这些结果指向一个强耦合的声学分支，这是在前向散射方向达到峰值，并具有重要意义的运输和配对在高T $_c$铜酸盐。
The nature of the pseudogap and its relationship with superconductivity are one of the central issues of cuprate superconductors. Recently, a possible scenario has been proposed that the pseudogap state is a distinct phase characterized by spontaneous rotational symmetry breaking called "nematicity" based on transport and magnetic susceptibility measurements, where the symmetry breaking was observed below the pseudogap temperature $T^*$. Here, we report a temperature-dependent ARPES study of nematicity in slightly overdoped Bi${}_{1.7}$Pb${}_{0.5}$Sr${}_{1.9}$CaCu${}_2$O${}_{8+δ}$ triggered by…
Anisotropic dressing of charge-carriers in the electron-doped cuprate superconductor Sm(1.85)Ce(0.15)CuO(4) from angle-resolved photoemission measurements
