Local Electronic Structures In Heavy-fermion Superconductor CeCoIn₅

As an important part of superconducting system, heavy-fermion superconductors have been extensively studied in condensed matter physics, especially for CeCoIns, which belongs to the famous Ce-115 family, and has the highest Tc≈2.3K in all Ce-based superconductors at ambient pressure. CeCoIn₅ shares many similarities with the cuprate superconductors as well as the newly discovered pnictide superconductors, for example, the quasi-two-dimensional Fermi surfaces （FS） and the competition between antiferromagnetism （AF） and superconductivity. It is hence generally believed that superconductivity in CeCoIn₅ is driven by strong AF spin fluctuations. Many experiments and theoretical calculations indeed have pointed to an unconventional d-wave pairing. Recently, a new spectroscopic technique was developed based on high-resolution scanning tunneling microscopy （STM）. It shows that the quasiparticle interference （QPI） resulting from CeCoIn₅ may support the dx²-y² wave pairing symmetry. To confirm the pairing symmetry, we start from the hybridized quasiparticle bands, applying the T-matrix approach and Green’s function to calculate the impurity-induced resonance state near the Fermi energy at both weak and strong impurity scattering. The impurity-induced resonance states arise near the Fermi energy at both dx²-y² and dxy wave, but the spatial modulation of the local density of states （LDOS） are completely different. At weak scattering strength, we found that the spatial modulation of the impurity-induced resonance state resembled the newly STM experiment. At the strong scattering strength, the spatial pattern of both dx²-y² and dxy pairings are strongly modulated by the nodal line of the gap structures. This unique property, combined with the experiments can verify the dx²-y² pairing symmetry in CeCoIns superconductor. We also believe that the features of impurity-induced resonance states and their spatial modulation can be applied to other Ce-based heavy-fermion superconductors so as to identify their pairing symmetry and understand the underlying unconventional superconductivity.