The single-layered ruthenate Sr₂RuO₄ is presented as a potential spin-triplet superconductor with an order parameter that may break time-reversal invariance and host half-quantized vortices with Majorana zero modes. Although the actual nature of the superconducting state is still a matter of controversy, it is believed to condense from a metallic state that is well described by a conventional Fermi liquid. In this work we use a combination of Fourier transform scanning tunnelling spectroscopy (FT-STS) and momentum-resolved electron energy loss spectroscopy (M-EELS) to probe interaction effects in the normal state of Sr₂RuO₄. Our high-resolution FT-STS data show signatures of the β-band with a distinctly quasi-one-dimensional (1D) character. The band dispersion reveals surprisingly strong interaction effects that dramatically renormalize the Fermi velocity, suggesting that the normal state of Sr₂RuO₄ is that of a ‘correlated metal’ where correlations are strengthened by the quasi-1D nature of the bands. In addition, kinks at energies of approximately 10 meV, 38 meV and 70 meV are observed. By comparing STM and M-EELS data we show that the two higher energy features arise from coupling with collective modes. The strong correlation effects and the kinks in the quasi-1D bands could provide important information for understanding the superconducting state.

中文翻译：

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Sr2RuO4的准一维带中的准粒子干扰和强电子模式耦合

单层钌酸Sr ₂ RuO ₄被表示为具有潜在参数的自旋三重态超导体，其阶数参数可能会打破时间反转不变性，并以马约拉那零模式承载半量化涡旋。尽管超导状态的实际性质仍是一个有争议的问题，但据信它是从常规费米液体充分描述的金属状态中凝结而来的。在这项工作中，我们结合使用傅里叶变换扫描隧道光谱（FT-STS）和动量分辨电子能量损失谱（M-EELS）来探测Sr ₂ RuO ₄正常状态下的相互作用效应。我们的高分辨率FT-STS数据显示具有明显准一维（1D）字符的β波段签名。谱带分散显示出令人惊讶的强大相互作用效应，该效应极大地使费米速度重新归一化，这表明Sr ₂ RuO ₄的正常态是“相关金属”的态，其中相关性由于谱带的准1D性质而得到增强。另外，观察到约 10meV， 38meV和70meV的能量的扭结 。通过比较STM和M-EELS数据，我们表明两个较高的能量特征是通过与集体模式耦合而产生的。强大的相关效应和准一维带的扭结可为理解超导状态提供重要信息。