Visualizing Nodal Heavy Fermion Superconductivity in CeCoIn5

TL;DR

This study uses advanced spectroscopic techniques to visualize how heavy-fermion excitations evolve and give rise to d-wave superconductivity in CeCoIn5, revealing pseudogap-like behavior and pairing symmetry.

Contribution

It extends high-resolution STM methods to low temperatures, demonstrating the development of superconductivity within composite excitations and identifying its nodal d-wave nature in CeCoIn5.

Findings

Spectral weight suppression near Fermi energy before superconductivity

Pseudogap-like state observed in heavy-fermion spectrum

Confirmation of nodal d-wave pairing symmetry

Abstract

Understanding the origin of superconductivity in strongly correlated electron systems continues to be at the forefront of unsolved problems in all of physics. Among the heavy f-electron systems, CeCoIn5 is one of the most fascinating, as it shares many of the characteristics of correlated d-electron high-Tc cuprate and pnictide superconductors, including the competition between antiferromagnetism and superconductivity. While there has been evidence for unconventional pairing in this compound, high-resolution spectroscopic measurements of the superconducting state have been lacking. Previously, we have used high-resolution scanning tunneling microscopy techniques to visualize the emergence of heavy-fermion excitations in CeCoIn5 and demonstrate the composite nature of these excitations well above Tc. Here we extend these techniques to much lower temperatures to investigate how superconductivity develops within a strongly correlated band of composite excitations. We find the spectrum of heavy excitations to be strongly modified just prior to the onset of superconductivity by a suppression of the spectral weight near the Fermi energy, reminiscent of the pseudogap state in the cuprates. By measuring the response of superconductivity to various perturbations, through both quasiparticle interference and local pair-breaking experiments, we demonstrate the nodal d-wave character of superconducting pairing in CeCoIn5.