RT Journal Article
SR Electronic
T1 Fully gapped superconductivity with no sign change in the prototypical heavy-fermion CeCu_{2}Si_{2}
JF Science Advances
JO Sci Adv
FD American Association for the Advancement of Science
SP e1601667
DO 10.1126/sciadv.1601667
VO 3
IS 6
A1 Yamashita, Takuya
A1 Takenaka, Takaaki
A1 Tokiwa, Yoshifumi
A1 Wilcox, Joseph A.
A1 Mizukami, Yuta
A1 Terazawa, Daiki
A1 Kasahara, Yuichi
A1 Kittaka, Shunichiro
A1 Sakakibara, Toshiro
A1 Konczykowski, Marcin
A1 Seiro, Silvia
A1 Jeevan, Hirale S.
A1 Geibel, Christoph
A1 Putzke, Carsten
A1 Onishi, Takafumi
A1 Ikeda, Hiroaki
A1 Carrington, Antony
A1 Shibauchi, Takasada
A1 Matsuda, Yuji
YR 2017
UL http://advances.sciencemag.org/content/3/6/e1601667.abstract
AB In exotic superconductors, including high-Tc copper oxides, the interactions mediating electron Cooper pairing are widely considered to have a magnetic rather than a conventional electron-phonon origin. Interest in this exotic pairing was initiated by the 1979 discovery of heavy-fermion superconductivity in CeCu2Si2, 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. We report low-temperature specific heat, thermal conductivity, and magnetic penetration depth measurements in CeCu2Si2, 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.