Abstract
Local quasiparticle states around impurities provide essential insight into the mechanism of unconventional superconductivity, especially when the candidate materials are proximate to an antiferromagnetic Mott-insulating phase. While such states have been reported in atom-based cuprates and iron-based compounds, they are unexplored in organic superconductors which feature tunable molecular orientation. Here we employ scanning tunneling microscopy and spectroscopy to reveal multiple forms of robustness of an exotic s-wave superconductivity in epitaxial Rb3C60 films against merohedral disorder, non-magnetic single impurities and step edges at the atomic scale. Yu-Shiba-Rusinov (YSR) states, induced by deliberately incurred Fe adatoms that act as magnetic scatterers, have also been observed. The YSR bound states show abrupt spatial decay and vary in energy with the Fe adatom registry. These results and a doping-dependent study of superconductivity point towards local electron pairing in which the multiorbital electronic correlations and intramolecular phonons together drive the high-temperature superconductivity of doped fullerenes.
Highlights
Local quasiparticle states around impurities provide essential insight into the mechanism of unconventional superconductivity, especially when the candidate materials are proximate to an antiferromagnetic Mott-insulating phase
Unlike atom-based superconductors, an organic superconductor is a synthetic molecule-based compound that uniquely exhibits additional degrees of freedom related to its molecular orientation
The fullerides represent an unusual category of organic superconductors in which the multiorbital electronic correlations and electron–phonon interactions are both suggested to be significant to reach high-Tc superconductivity[33,34]
Summary
Local quasiparticle states around impurities provide essential insight into the mechanism of unconventional superconductivity, especially when the candidate materials are proximate to an antiferromagnetic Mott-insulating phase While such states have been reported in atombased cuprates and iron-based compounds, they are unexplored in organic superconductors which feature tunable molecular orientation. The fullerides represent an unusual category of organic superconductors in which the multiorbital electronic correlations and electron–phonon interactions are both suggested to be significant to reach high-Tc superconductivity[33,34] Under this context, a systematic study of impurity effects on superconductivity of doped fullerenes would provide justification of the previously advocated s-wave pairing symmetry[35,36,37], as well as advance the understanding of the superconducting state.
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