Tuning Tomonaga-Luttinger Liquid in the Topological Edge Channel of bilayer FeSeS by Chemical Pressure

Iron chalcogenide FeSe exhibits nematicity without long-range magnetic order, which is shown to be a quantum paramagnet dominated by antiferromagnetic (AFM) fluctuations, offering an ideal platform to probe the interplay of magnetism, nematicity, and superconductivity. In epitaxial thin film of FeSe grown on SrTiO₃(001) by molecular beam epitaxy, we have reported robust edge states whose density of states follows a universal scaling with both energy and temperature, characteristic of Tomonaga-Luttinger liquid (TLL) behavior [Nano Letters 21,6253 (2021)]. In this work, by the isovalent substitution of S into epitaxial bilayer FeSe films on SrTiO₃(001) substrates, chemical pressure is applied to tune the TLL behavior in the topological edge channels. Using scanning tunneling microscopy and spectroscopy, we observe similar edge states at the Fermi level for different S concentrations. The experimental V-shaped dI/dV tunneling spectra are fitted using the TLL model. We find that the TLL parameter decreases as S concentration increases, suggesting increasing electron-electron interactions. These results demonstrate that chemical pressure is an effective method to tune the interplay between topology and AFM fluctuations in Fe chalcogenides.