Low-energy electron-mode couplings in the surface bands of Sr2RuO4 revealed by laser-based angle-resolved photoemission spectroscopy

The low-energy electron-mode couplings are of interest in the study of superconductors as they could be the essential excitations to form electron pairs. The authors use laser-based angle-resolved photoemission spectroscopy and find a kink structure around 8 meV in the bands of Sr${}_{2}$RuO${}_{4}$. It is most pronounced for the $d$${}_{x\phantom{\rule{0}{0ex}}y}$ orbital, which implies that its mechanism is the electron coupling to ferromagnetic spin fluctuations. The results suggest that the ferromagnetic fluctuations are a promising candidate for the pairing mechanism in the unconventional superconductivity of Sr${}_{2}$RuO${}_{4}$.