Impurity effects on electron–mode coupling in high-temperature superconductors

Despite years of intensive research on copper oxide superconductors with high transition temperatures (Tc), the driving force of superconductivity has not yet been clarified. Angle-resolved photoemission spectroscopy (ARPES)1,2,3 measurements have uncovered an important contribution of lattice vibrations (phonons) to superconductivity, sparking a fierce debate on the nature of the ‘glue’—phonons or magnetic excitations—binding together the superconducting Cooper pairs1,2,3,4,5,6,7,8,9,10,11. However, it is difficult to distinguish these two pairing forces owing to their similar energy scales. Here, we propose a fresh approach to investigate the origin of many-body interactions in these superconductors: an impurity-substitution effect on the low-energy dynamics, which is a magnetic analogue of the isotope effect used for classical superconductors. Our ARPES results reveal that the impurity-induced changes in the electron self-energy show a good correspondence to those of magnetic excitations12,13,14,15,16,17,18, indicating the importance of spin fluctuations to electron pairing in the high-Tc superconductors.