revealed by spatially and angle-resolved photoemission spectroscopy

摘要： 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 ?uctuations have been observed. As the precursor to this order, nematic ?uctuations emerge before nematicity, providing favorable ground to study how nematic order modi?es 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 ?uctuations and electronic structure in an optimally doped BaFe2(As1?xPx )2 (x ～ 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 ?uctuating nematic order. These results provide direct evidence for spatial nematic ?uctuations in the optimal doping regime of iron-based superconductors.