1. Fully gapped superconductivity with no sign change in the prototypical heavy-fermion CeCu2Si2
- Author
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Carsten Putzke, Yoshifumi Tokiwa, Christoph Geibel, Hirale S. Jeevan, Takaaki Takenaka, J. A. Wilcox, Takuya Yamashita, Toshiro Sakakibara, Antony Carrington, Takasada Shibauchi, Hiroaki Ikeda, Yuichi Kasahara, Daiki Terazawa, Takafumi Onishi, Shunichiro Kittaka, Yuji Matsuda, Silvia Seiro, M. Konczykowski, Yuta Mizukami, Kyoto University [Kyoto], Department of Advanced Materials Sciences, The University of Tokyo (UTokyo), University of Bristol [Bristol], Institute for Solid State Physics [Tokyo] (ISSP), Laboratoire des Solides Irradiés (LSI), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Max Planck Institute for Chemical Physics of Solids (CPfS), Max-Planck-Gesellschaft, Ritsumeikan University, Department of Physics, Kyoto University, and Kyoto University
- Subjects
Superconducting coherence length ,Superconductivity ,FOS: Physical sciences ,02 engineering and technology ,Electron ,01 natural sciences ,unconventional superconductors ,Superconductivity (cond-mat.supr-con) ,Condensed Matter - Strongly Correlated Electrons ,heavy-fermion materials ,Quantum mechanics ,Condensed Matter::Superconductivity ,0103 physical sciences ,Coulomb ,Antiferromagnetism ,010306 general physics ,pairing symmetry ,Computer Science::Databases ,Research Articles ,Condensed Matter::Quantum Gases ,Physics ,Multidisciplinary ,Condensed matter physics ,[PHYS.PHYS]Physics [physics]/Physics [physics] ,Strongly Correlated Electrons (cond-mat.str-el) ,Condensed Matter - Superconductivity ,SciAdv r-articles ,Fermi surface ,021001 nanoscience & nanotechnology ,Pairing ,Strongly Correlated Electrons ,0210 nano-technology ,Research Article ,Sign (mathematics) - Abstract
In exotic superconductors including high-$T_c$ copper-oxides, the interactions mediating electron Cooper-pairing are widely considered to have a magnetic rather than the conventional electron-phonon origin. Interest in such exotic pairing was initiated by the 1979 discovery of heavy-fermion superconductivity in CeCu$_2$Si$_2$, which exhibits strong antiferromagnetic fluctuations. A hallmark of unconventional pairing by anisotropic repulsive interactions is that the superconducting energy gap changes sign as a function of the electron momentum, often leading to nodes where the gap goes to zero. Here, we report low-temperature specific heat, thermal conductivity and magnetic penetration depth measurements in CeCu$_2$Si$_2$, demonstrating the absence of gap nodes at any point on the Fermi surface. Moreover, electron-irradiation experiments reveal that the superconductivity survives even when the electron mean free path becomes substantially shorter than the superconducting coherence length. This indicates that superconductivity is robust against impurities, implying that there is no sign change in the gap function. These results show that, contrary to long-standing belief, heavy electrons with extremely strong Coulomb repulsions can condense into a fully-gapped s-wave superconducting state, which has an on-site attractive pairing interaction., Comment: 8 pages, 5 figures + Supplement (3 pages, 5 figures)
- Published
- 2017