Fully gapped d-wave superconductivity in CeCu2Si2

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 115; no. 21; pp. 5343 - 5347
• Main Authors: Pang, Guiming, Smidman, Michael, Zhang, Jinglei, Jiao, Lin, Weng, Zongfa, Nica, Emilian M, Chen, Ye, Jiang, Wenbing, Zhang, Yongjun, Xie, Wu, Jeevan, Hirale S, Lee, Hanoh, Gegenwart, Philipp, Steglich, Frank, Si, Qimiao, Yuan, Huiqiu
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 22.05.2018
• Subjects: CeCu2Si2; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; heavy fermions; multiband superconducting pairing; penetration depth; Physical Sciences; science & technology - other topics; superconducting order parameter
• ISSN: 1091-6490; 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1720291115

The nature of the pairing symmetry of the first heavy fermion superconductor CeCu2Si2 has recently become the subject of controversy. While CeCu2Si2 was generally believed to be a d-wave superconductor, recent low-temperature specific heat measurements showed evidence for fully gapped superconductivity, contrary to the nodal behavior inferred from earlier results. Here, we report London penetration depth measurements, which also reveal fully gapped behavior at very low temperatures. To explain these seemingly conflicting results, we propose a fully gapped [Formula: see text] band-mixing pairing state for CeCu2Si2, which yields very good fits to both the superfluid density and specific heat, as well as accounting for a sign change of the superconducting order parameter, as previously concluded from inelastic neutron scattering results.The nature of the pairing symmetry of the first heavy fermion superconductor CeCu2Si2 has recently become the subject of controversy. While CeCu2Si2 was generally believed to be a d-wave superconductor, recent low-temperature specific heat measurements showed evidence for fully gapped superconductivity, contrary to the nodal behavior inferred from earlier results. Here, we report London penetration depth measurements, which also reveal fully gapped behavior at very low temperatures. To explain these seemingly conflicting results, we propose a fully gapped [Formula: see text] band-mixing pairing state for CeCu2Si2, which yields very good fits to both the superfluid density and specific heat, as well as accounting for a sign change of the superconducting order parameter, as previously concluded from inelastic neutron scattering results.