Extended Nuclear Quadrupole Resonance Study of the Heavy-Fermion Superconductor PuCoGa${}_5$

Abstract

PuCoGa${}_5$ has emerged as a prototypical heavy-fermion superconductor, with its transition temperature ($T_c\simeq 18.5$ K) being the highest amongst such materials. Nonetheless, a clear description as to what drives the superconducting pairing is still lacking, rendered complicated by the notoriously intricate nature of plutonium's 5$f$ valence electrons. Here, we present a detailed ${}^{69,71}$Ga nuclear quadrupole resonance (NQR) study of PuCoGa${}_5$, concentrating on the system's normal state properties near to $T_c$ and aiming to detect distinct signatures of possible pairing mechanisms. In particular, the quadrupole frequency and spin-lattice relaxation rate were measured for the two crystallographically inequivalent Ga sites and for both Ga isotopes, in the temperature range 1.6 K - 300 K. No evidence of significant charge fluctuations is found from the NQR observables. On the contrary, the low-energy dynamics is dominated by anisotropic spin fluctuations with strong, nearly critical, in-plane character, which are effectively identical to the case of the sister compound PuCoIn${}_5$. These findings are discussed within the context of different theoretical proposals for the unconventional pairing mechanism in heavy-fermion superconductors.

7 pages, 8 figures

References in corpus (7)

• Magnetism, superconductivity, and pairing symmetry in Fe-based superconductors
• Quantum critical state in a magnetic quasicrystal
• Spin susceptibility, phase diagram, and quantum criticality in the electron-doped high Tc Superconductor Ba[Fe(1-x)Co(x)]2As2
• Heavy electrons and the symplectic symmetry of spin
• Supplementary material to Heavy electrons and the symplectic symmetry of spin
• Unconventional Quantum Criticality due to Critical Valence Transition
• Anisotropic spin fluctuations and superconductivity in "115'' heavy fermion compounds: 59Co NMR study in PuCoGa5

Cited by in corpus (1)

• Probing magnetism in the vortex phase of PuCoGa${}_5$ by X-ray magnetic circular dichroism