Momentum Dependence of the Single-Particle Self-Energy and Fluctuation Spectrum of Slightly Underdoped Bi_2 Sr_2 CaCu_2 O_{8+\delta} from High Resolution Laser ARPES
Momentum Dependence of the Single-Particle Self-Energy and Fluctuation Spectrum of Slightly Underdoped Bi_2 Sr_2 CaCu_2 O_{8+\delta} from High Resolution Laser ARPES
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DOI：
10.1103/physrevb.81.174516
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发表时间：
2009-12
影响因子：
3.7
通讯作者：
Jin Mo Bok;J. Yun;Han-Yong Choi;Wen-tao Zhang;X. Zhou;C. Varma
中科院分区：
文献类型：
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作者：
Jin Mo Bok;J. Yun;Han-Yong Choi;Wen-tao Zhang;X. Zhou;C. Varma
我们推导出正常态角分辨单粒子自能$\Sigma（\theta，\omega）$和Eliashberg函数（即，用超高分辨激光角分辨光电子能谱（ARPES）测量了高温超导体Bi 2 Sr 2 CaCu 2 O 8+ δ的涨落谱及其与费米子耦合的乘积）2 α 2 F（\θ，\omega）。通过拟合ARPES动量分布曲线，提取了在稍微欠掺杂的Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$中，沿着沿着垂直于费米表面的几个切口，以相对于节点方向的倾斜角$\theta$的能量$\Sigma（\theta，\omega）$。然后，使用提取的自能量作为实验输入，$\alpha^2 F（\theta，\omega）$推导出由逆Eliashberg方程采用自适应最大熵方法。我们的主要新结果是Eliashberg函数2F（\theta，\omega）$对所有的$\theta$坍缩到一个单一的$\omega$函数上，直到截止能量，尽管$\theta$依赖于自能。因此，面内动量各向异性主要是由于各向异性带色散效应。所得到的Eliashberg函数有一个小的峰值在$\omega\approx0.05 $ eV和0.1 eV以上的角依赖性截止。它取约0.4 eV的本征截止值或带底能量相对于费米能在方向$\theta$，以较低者为准。F（\theta，\omega）$的角度无关性只与在晶格常数尺度上具有短相关长度的涨落谱一致。这意味着反铁磁涨落可能不是推导出的涨落谱的基础物理。
We deduce the normal state angle-resolved single-particle self-energy $\Sigma(\theta, \omega)$ and the Eliashberg function (i.e., the product of the fluctuation spectrum and its coupling to fermions) $\alpha^2 F(\theta,\omega)$ for the high temperature superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ from the ultra high resolution laser angle-resolved photoemission spectroscopy (ARPES). The self-energy $\Sigma(\theta, \omega)$ at energy $\omega$ along several cuts normal to the Fermi surface at the tilt angles $\theta$ with respect to the nodal direction in a slightly underdoped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ were extracted by fitting the ARPES momentum distribution curves. Then, using the extracted self-energy as the experimental input, the $\alpha^2 F(\theta,\omega)$ is deduced by inverting the Eliashberg equation employing the adaptive maximum entropy method. Our principal new result is that the Eliashberg function $\alpha^2F(\theta,\omega)$ collapse for all $\theta$ onto a single function of $\omega$ up to the upper cut-off energy despite the $\theta$ dependence of the self-energy. The in-plane momentum anisotropy is therefore predominantly due to the anisotropic band dispersion effects. The obtained Eliashberg function has a small peak at $\omega\approx0.05$ eV and flattens out above 0.1 eV up to the angle-dependent cut-off. It takes the intrinsic cut-off of about 0.4 eV or the energy of the bottom of the band with respect to the Fermi energy in the direction $\theta$, whichever is lower. The angle independence of the $\alpha^2 F(\theta,\omega)$ is consistent only with the fluctuation spectra which have the short correlation length on the scale the lattice constant. This implies among others that the antiferromagnetic fluctuations may not be underlying physics of the deduced fluctuation spectrum.