Abstract
In the generic phase diagram of heavy fermion systems, tuning an external parameter such as hydrostatic or chemical pressure modifies the superconducting transition temperature. The superconducting phase forms a dome in the temperature—tuning parameter phase diagram, which is associated with a maximum of the superconducting pairing interaction. Proximity to antiferromagnetism suggests a relation between the disappearance of antiferromagnetic order and superconductivity. We combine muon spin rotation, neutron scattering, and x-ray absorption spectroscopy techniques to gain access to the magnetic and electronic structure of CeCo(In1−xCdx)5 at different time scales. Different magnetic structures are obtained that indicate a magnetic order of itinerant character, coexisting with bulk superconductivity. The suppression of the antiferromagnetic order appears to be driven by a modification of the bandwidth/carrier concentration, implying that the electronic structure and consequently the interplay of superconductivity and magnetism is strongly affected by hydrostatic and chemical pressure.
Highlights
Understanding the interactions between superconductivity and magnetism in heavy fermion systems is one of the greatest challenges of condensed matter physics, often presented as a key to unveil the mechanism of unconventional superconductivity
A variation of the Ruderman-Kittel-Kasuya-Yoshida (RKKY) coupling is unlikely to be the cause of the suppression of the AFM phase as no ferromagnetism was reported under higher pressures[24]
The SC and AFM transition temperatures for samples with various cadmium concentrations were used to determine the position of the samples into the phase diagram and their corresponding negative pressure (Fig. 1)
Summary
Understanding the interactions between superconductivity and magnetism in heavy fermion systems is one of the greatest challenges of condensed matter physics, often presented as a key to unveil the mechanism of unconventional superconductivity. At least three different mechanisms can “delocalize” the Ce 4f electrons: (i) the Kondo effect[21], (ii) an increase in cerium valence[22], and (iii) the formation/broadening of an electronic band of partial Ce 4f character (Mott delocalization)[23]. Each of these effects can independently introduce the Ce 4f electrons into the Fermi surface. The suppression of antiferromagnetism must be ascribed to a “delocalization” of itinerant Ce 4f electrons
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