Nematicity, where rotational symmetry is broken while translational symmetry is conserved, is prevalent in high-temperature superconductors. In particular, nematic quantum critical point has been universally found near the optimum doping of the superconducting dome of several iron-based superconductor families. In such a regime, evidence for strong nematic fluctuations have been observed. As the precursor to this order, nematic fluctuations emerge before nematicity, providing favorable ground to study how nematic order modifies the electronic structure in the absence of structural distortion. Here we use spatially resolved angle-resolved photoemission spectroscopy to investigate the correlation between the onset of nematic fluctuations and electronic structure in an optimally doped ${\mathrm{BaFe}}_2{\left({\mathrm{As}}_{1-x}{\mathrm{P}}_x\right)}_2$ ($x\sim 0.3$) superconductor. We reveal a strong spatially varying anisotropy of the Fermi surface on a length scale of tens of microns with strong correlation between the changes in the hole and electron Fermi pockets, consistent with the variations expected in the presence of fluctuating nematic order. These results provide direct evidence for spatial nematic fluctuations in the optimal doping regime of iron-based superconductors.

中文翻译：

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空间和角度分辨光发射光谱揭示的BaFe2（As1-xPx）2的空间向列波动

向列性在高温超导体中普遍存在，其中旋转对称性被破坏，而平移对称性被保留。特别是，在几个铁基超导体族的超导圆顶的最佳掺杂附近普遍发现了向列型量子临界点。在这种情况下，已经观察到强烈的向列波动的证据。作为此序的先兆，向列波动先于向列出现，为研究向列序如何在不存在结构畸变的情况下修饰电子结构提供了有利依据。在这里，我们使用空间分辨角分辨光电子能谱研究在最佳掺杂中向列波动的发生与电子结构之间的相关性。${\mathrm{钡铁}}_2{（{如}_{\mathrm{1个}-X}{\mathrm{P}}_X）}_2$ （$X〜0.3$）超导体。我们揭示了几十微米长尺度上费米表面的强烈的空间变化各向异性，在空穴和电子费米腔的变化之间有很强的相关性，这与在向列型波动时预期的变化一致。这些结果为铁基超导体的最佳掺杂方式中的空间向列波动提供了直接证据。