Superconducting gap symmetry from the quasiparticle interference in the heavy fermion superconductor CeCoIn5

One of the most difficult issues in the heavy Fermion superconductors like the 115 compounds CeMIn5 (M=Co,Ir,Rh) is the identification of the symmetry of superconducting order parameter. The ambiguity between dxy and dx2-y2 symmetry remained from earlier specific heat and thermal transport investigations has been resolved in favor of the latter by the observation of a spin resonance that can occur only in dx2-y2 symmetry. However these methods are all indirect and depend considerably on theoretical interpretation. We presented the theory for the quasiparticle interference (QPI) in the heavy Fermion superconductor CeCoIn5 as a direct method to confirm the d-wave gap symmetry. We calculate the QPI pattern for both magnetic and nonmagnetic impurities. By comparing the effect of the possible d-wave superconducting order parameters on QPI, the characteristic differences are found which may be identified by STM method. Our results propose that quasiparticle interference (QPI) and scanning tunneling microscopy (STM) can give a direct fingerprint of the superconducting gap in real space which may lead to a definite conclusion on its symmetry for CeCoIn5 and related 115 compounds.