Impurity-induced bound states as a signature of pairing symmetry in multiband superconducting CeCu₂Si₂

Abstract

The notion of multiband superconductivity with dominant two-gap features has been recently applied to the unconventional superconductor CeCu₂Si₂ for challenging the previously accepted concept of nodal d-wave pairing. In the proposed study, the realistic multiband Fermi surface topology of CeCu₂Si₂ was obtained through first-principles calculations, and analysis was conducted with an effective two-band hybridization model including detailed band structure. Within the T-matrix approximation, the obtained calculation results show that different pairing candidates, including fully gapped s-wave, loop-nodal s-wave, and d-wave pairings, could yield qualitatively distinct features characterized by impurity-induced bound states. These features can be verified through high-resolution scanning tunneling microscopy or spectroscopy and provide corroborative justification that would be beneficial for the ongoing research regarding the superconducting gap symmetry of CeCu₂Si₂ at ambient pressure.

Keywords

heavy-fermion superconductivity / pairing symmetry / impurity effect / local density of states

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