Superconductivity In Heavy Fermion Superconductor Research Articles

Heavy Electron Superconductors in Terms of Block Spin Phenomenology

We investigate the relationship between superconductivity and spin glasses, which were observed to be coexistent in heavy fermion superconductors (HFSs). We begin by explaining the phase of spin glass using concepts of finite-sized block spin. We then introduce the phase of superconductivity in HFSs as collective Cooper pairing, that is, the pairing of block spins with net spin = 1/2, each of which is comprised of a large number of random spins that together produce a majority spin direction. The superconducting Bardeen-Cooper-Schrieffer (BCS)-type phonon-mediated electron-electron interaction is substituted for the BCS-type electron-electron interaction mediated by phonon-enhanced spin flips previously suggested by us. An effective charge of any value stemming from an electron attached to the flux of an electric field can be referred to as a composite charge. The distinguished difference between ours and the original BCS model is the following: (i) another BCS-type interaction, (ii) bare electrons that are substituted for block spins with net spin = 1/2 and net charge = e in the presence of electric fields, and (iii) Fermi-Dirac distributions that are replaced by a new distribution called as Brillouin distribution.

Magnetism and superconductivity in heavy fermion superconductor

Abstract Zero field (ZF) and transverse field (TF) muon spin relaxation and rotation ( μ SR ) experiments have been carried out in the Cd-doped heavy fermion superconductor CeCoIn 5 to investigate its superconducting state. The ZF- μ SR results in CeCo ( In 0.97 Cd 0.03 ) 5 revealed that no spontaneous magnetic field was induced below its superconducting transition temperature ( T c ), indicating no evidence for time reversal symmetry breaking. The muon Knight shifts obtained from TF- μ SR measurements decrease significantly below T c , consistent with a spin-singlet state as in the parent compound CeCoIn 5 , which is a d-wave superconductor.

Neutron scattering studies on heavy fermion superconductors

We present the experimental evidence for the strong interplay between magnetism and superconductivity in heavy fermion superconductors. In UPd 2Al 3, we found the superconducting gap appearing in magnetic excitation spectra. We also report the long-range magnetic correlation of the weak antiferromagnetism in UPt 3 below 20 mK, which would be a precursive phenomenon of the static ordering.

Magnetism and superconductivity in heavy-fermion superconductors with a partially gapped Fermi surface

A large-degeneracy model is applied to study antiferromagnetic order and superconductivity in heavy-fermion superconductors with a partially gapped Fermi surface. An antiferromagnetic order opens a gap on those parts of the Fermi surface where nesting takes place. Below the Neel temperature, antiferromagnetic moments of f atoms are anomalously small ( approximately 10-2 mu B). The rest of the Fermi surface becomes gapped due to superconductivity stimulated by the long-range antiferromagnetic order. The superconducting gap is anisotropic and vanishes on lines. A satisfactory agreement with experimental data for URu2Si2 is obtained.