Competing magnetic orders in the superconducting state of heavy-fermion CeRhIn<sub>5</sub>.

Rosa, P F S; Kang, J; Luo, Yongkang; Wakeham, N; Bauer, E D; Ronning, F; Fisk, Z; Fernandes, R M et al. · Proc Natl Acad Sci U S A · 2017

basic_science · Level V

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Abstract

Applied pressure drives the heavy-fermion antiferromagnet CeRhIn<sub>5</sub> toward a quantum critical point that becomes hidden by a dome of unconventional superconductivity. Magnetic fields suppress this superconducting dome, unveiling the quantum phase transition of local character. Here, we show that [Formula: see text] magnetic substitution at the Ce site in CeRhIn<sub>5</sub>, either by Nd or Gd, induces a zero-field magnetic instability inside the superconducting state. This magnetic state not only should have a different ordering vector than the high-field local-moment magnetic state, but it also competes with the latter, suggesting that a spin-density-wave phase is stabilized in zero field by Nd and Gd impurities, similarly to the case of Ce<sub>0.95</sub>Nd<sub>0.05</sub>CoIn<sub>5</sub> Supported by model calculations, we attribute this spin-density wave instability to a magnetic-impurity-driven condensation of the spin excitons that form inside the unconventional superconducting state.