Bandstructure Engineering by Surface Water Dosing on SrFe₂As₂

Fe-based superconductors represent a fascinating class of materials, extensively studied for their complex interplay of superconductivity, magnetism, spin density waves, and nematicity, along with the interactions among these orders. An intriguing and yet unexplained phenomenon observed in Fe-based superconductors is the emergence of superconductivity below 25K in the non-superconducting parent compound SrFe₂As₂ following exposure to water at its surface. In this study, we employed in-situ angle-resolved photoemission spectroscopy and low-energy electron diffraction to meticulously examine the electronic structure evolution of SrFe₂As₂ upon in-situ water dosing. Our findings indicate that water dosing markedly attenuates the SDW phase and surface Sr reconstruction, yet preserves the nematic order in the SrFe₂As₂. Furthermore, we detected an enhancement in the spectral weight of bands near the Fermi level. Our observations highlight the critical role of the intricate interplay among various orders induced by water dosing, which effectively modifies the band structure and favor the emergence of superconductivity in SrFe₂As₂.