Walker M, Scott K, Boyle T J, Byland J K, Bötzel S, Zhao Z, Day R P, Zhdanovich S, Gorovikov S, Pedersen T M, Klavins P, Damascelli A, Eremin I M, Gozar A, Taufour V, da Silva Neto E H
Department of Physics and Astronomy, University of California, Davis, CA USA.
Department of Physics, Yale University, New Haven, CT USA.
NPJ Quantum Mater. 2023;8(1):60. doi: 10.1038/s41535-023-00592-5. Epub 2023 Oct 19.
FeSeS remains one of the most enigmatic systems of Fe-based superconductors. While much is known about the orthorhombic parent compound, FeSe, the tetragonal samples, FeSeS with > 0.17, remain relatively unexplored. Here, we provide an in-depth investigation of the electronic states of tetragonal FeSeS, using scanning tunneling microscopy and spectroscopy (STM/S) measurements, supported by angle-resolved photoemission spectroscopy (ARPES) and theoretical modeling. We analyze modulations of the local density of states (LDOS) near and away from Fe vacancy defects separately and identify quasiparticle interference (QPI) signals originating from multiple regions of the Brillouin zone, including the bands at the zone corners. We also observe that QPI signals coexist with a much stronger LDOS modulation for states near the Fermi level whose period is independent of energy. Our measurements further reveal that this strong pattern appears in the STS measurements as short range stripe patterns that are locally two-fold symmetric. Since these stripe patterns coexist with four-fold symmetric QPI around Fe-vacancies, the origin of their local two-fold symmetry must be distinct from that of nematic states in orthorhombic samples. We explore several aspects related to the stripes, such as the role of S and Fe-vacancy defects, and whether they can be explained by QPI. We consider the possibility that the observed stripe patterns may represent incipient charge order correlations, similar to those observed in the cuprates.
FeSeS仍然是铁基超导体中最神秘的体系之一。虽然人们对正交结构的母体化合物FeSe了解很多，但对于四方结构的样品，即硫含量大于0.17的FeSeS，仍相对缺乏研究。在此，我们利用扫描隧道显微镜和光谱（STM/S）测量，结合角分辨光电子能谱（ARPES）和理论建模，对四方结构的FeSeS的电子态进行了深入研究。我们分别分析了靠近和远离铁空位缺陷处的局域态密度（LDOS）调制，并识别出来自布里渊区多个区域（包括区角处的能带）的准粒子干涉（QPI）信号。我们还观察到，对于费米能级附近的态，QPI信号与更强的LDOS调制共存，其周期与能量无关。我们的测量进一步揭示，这种强图案在STS测量中表现为局部具有二重对称性的短程条纹图案。由于这些条纹图案与围绕铁空位的四重对称QPI共存，其局部二重对称性的起源必然不同于正交结构样品中向列相的起源。我们探讨了与条纹相关的几个方面，如硫和铁空位缺陷的作用，以及它们是否可以用QPI来解释。我们考虑了观察到的条纹图案可能代表类似于铜酸盐中观察到的初始电荷序关联的可能性。
