The interplay of different electronic phases underlies the physics of unconventional superconductors. One of the most intriguing examples is a high-temperature superconductor, FeTe_1 – xSe_x (refs. ^{1,2,3,4,5,6,7,8,9,10,11}). This superconductor undergoes both a topological transition^3,4, linked to the electronic band inversion, and an electronic nematic phase transition, associated with rotation symmetry breaking, around the same Se composition where the superconducting transition temperature peaks^12,13. In this regime, nematic fluctuations and symmetry-breaking strain could be important, but this is yet to be fully explored. Using spectroscopic-imaging scanning tunnelling microscopy, we study the electronic nematic transition in FeTe_1 – xSe_x as a function of composition. Near the critical Se composition, we find electronic nematicity in nanoscale regions. The superconducting coherence peaks are suppressed in areas where static nematic order is the strongest. By analysing atomic displacement in scanning tunnelling microscopy topographs, we find that small anisotropic strain can give rise to these strongly nematic localized regions. Our experiments reveal a tendency of FeTe_1 – xSe_x, near x ≈ 0.45, to form puddles hosting static nematic order, suggestive of nematic fluctuations pinned by structural inhomogeneity, and demonstrate the effect of anisotropic strain on superconductivity in this regime.

不同电子相的相互作用是非常规超导体物理学的基础。最有趣的例子之一是高温超导体 FeTe _{1 –  x} Se _x（参考文献^{1,2,3,4,5,6,7,8,9,10,11}）。这种超导体经历与电子能带反转相关的拓扑转变^3,4和与旋转对称性破坏相关的电子向列相转变，围绕超导转变温度达到峰值的相同 Se 成分^12,13. 在这种情况下，向列波动和对称破坏应变可能很重要，但这还有待充分探索。使用光谱成像扫描隧道显微镜，我们研究了 FeTe _{1 -  x} Se _x中的电子向列转变与成分的关系。在临界硒成分附近，我们发现纳米级区域存在电子向列性。超导相干峰在静态向列顺序最强的区域被抑制。通过分析扫描隧道显微镜形貌图中的原子位移，我们发现小的各向异性应变可以产生这些强烈的向列局部区域。我们的实验揭示了 FeTe _{1 –  x} Se _x的趋势，接近x ≈ 0.45，形成具有静态向列顺序的水坑，表明结构不均匀性导致向列波动，并证明了各向异性应变对这种状态下超导性的影响。