Emergent loop-nodal s${}_{\pm }$-wave superconductivity in CeCu${}_2$Si${}_2$: similarities to the iron-based superconductors

Abstract

Heavy-fermion superconductors are prime candidates for novel electron-pairing states due to the spin-orbital coupled degrees of freedom and electron correlations. Superconductivity in CeCu${}_2$Si${}_2$ discovered in 1979, which is a prototype of unconventional (non-BCS) superconductors in strongly correlated electron systems, still remains unsolved. Here we provide the first report of superconductivity based on the advanced first-principles theoretical approach. We find that the promising candidate is an $s_{\pm }$-wave state with loop-shaped nodes on the Fermi surface, different from the widely expected line-nodal $d$-wave state. The dominant pairing glue is magnetic but high-rank octupolar fluctuations. This system shares the importance of multi-orbital degrees of freedom with the iron-based superconductors. Our findings reveal not only the long-standing puzzle in this material, but also urge us to reconsider the pairing states and mechanisms in all heavy-fermion superconductors.

5 pages, 2 figures

References in corpus (9)

• Signatures of valence fluctuations in CeCu2Si2 under high pressure
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• Modelling the Localized to Itinerant Electronic Transition in the Heavy Fermion System CeIrIn5
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• Emergent Rank-5 'Nematic' Order in URu2Si2
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• Valence Instability and Superconductivity in Heavy Fermion Systems
• Determining the in-plane orientation of the ground-state orbital of CeCu2Si2
• Unconventional Quantum Criticality due to Critical Valence Transition

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• Thermodynamic study of gap structure and pair-breaking effect by magnetic field in the heavy-fermion superconductor CeCu2Si2
• Hexadecapole fluctuation mechanism for s-wave heavy fermion superconductor CeCu2Si2: Interplay between intra- and inter-orbital Cooper pairs
• Magnetic and superconducting properties on S-type single-crystal CeCu${}_2$Si${}_2$ probed by ${}^{63}$Cu nuclear magnetic resonance and nuclear quadrupole resonance
• Structural, magnetic, and electronic evolution of the spin-ladder system BaFe${}_2$S${}_{3-x}$Se${}_x$ with isoelectronic substitution
• Fermi Surfaces in the Antiferromagnetic, Paramagnetic and Polarized Paramagnetic States of CeRh2Si2 Compared with Quantum Oscillation Experiments
• Revealing sign-reversal $s^{+-}$-wave pairing by quasiparticle interference in the heavy-fermion superconductor CeCu${}_2$Si${}_2$