Superconductivity in the heavy-fermion compound CeCu2Si2 is a prototypical example of Cooper pairs formed by strongly correlated electrons. For more than 30 years, it has been believed to arise from nodal d-wave pairing mediated by a magnetic glue. Here, we report a detailed study of the specific heat and magnetization at low temperatures for a high-quality single crystal. Unexpectedly, the specific-heat measurements exhibit exponential decay with a two-gap feature in its temperature dependence, along with a linear dependence as a function of magnetic field and the absence of oscillations in the field angle, reminiscent of multiband full-gap superconductivity. In addition, we find anomalous behavior at high fields, attributed to a strong Pauli paramagnetic effect. A low quasiparticle density of states at low energies with a multiband Fermi-surface topology would open a new door into electron pairing in CeCu2Si2.
@article{arxiv.1307.3499,
title = {Multiband superconductivity with unexpected deficiency of nodal quasiparticles in CeCu2Si2},
author = {Shunichiro Kittaka and Yuya Aoki and Yasuyuki Shimura and Toshiro Sakakibara and Silvia Seiro and Christoph Geibel and Frank Steglich and Hiroaki Ikeda and Kazushige Machida},
journal= {arXiv preprint arXiv:1307.3499},
year = {2014}
}
Comments
5 pages, 4 figures (main text) + 5 pages, 6 figures (supplemental material), published in Phys. Rev. Lett