Violation of Pauli-Clogston limit in the heavy-fermion superconductor CeRh2As2: Duality of itinerant and localized 4f electrons

Abstract

We theoretically propose a mechanism to understand the violation of the Pauli-Clogston limit for the upper critical field Hc2 observed in the Ce bearing heavy Fermion material CeRh2As2 from the view point of spin singlet pairing. It is based on a duality concept, the dual simultaneous aspects of an electron: The itinerant part and localized part of quasiparticles (QPs) originated from the 4f electrons of the Ce atoms. While the itinerant QPs directly participate in forming the Cooper pairs, the localized QPs exert the internal field so as to oppose the applied field through the antiferromagnetic exchange interaction between them. This is inherent in the dense Kondo lattice system in general. We argue that this mechanism can be applied not only to the locally noncentrosymmetric material CeRh2As2, but also to globally inversion symmetry broken Ce-based materials such as CePt3Si. Moreover, we point out that it also works for strongly Pauli-limit-violated spin triplet pairing systems, such as UTe2.

Source-reported materials — not catalogue approval

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