The temperature, field, and field-orientation dependences of the electronic specific heat Ce of the ironpnictide superconductor KFe2As2 have been investigated. Thermodynamic evidence of the presence of line nodes is obtained from the T and H linear dependences of Ce/T in the low-T and low-H region. Under a magnetic field rotated within the tetragonal ab plane, a fourfold oscillation is observed in Ce with a sign change at 0.08Tc. On the basis of the Doppler-shift analysis, the observed Ce minima in H // [100] at low T indicate the presence of line nodes somewhere on the Fermi surface where the Fermi velocity is parallel to the [100] direction; this is consistent with the octet-line-node scenario proposed recently by a photoemission experiment. In addition, the low-T Ce/T exhibits an unusual upturn on cooling at moderate fields only for H // ab, which is understood in terms of the strong Pauli paramagnetic effect on multiband superconductivity.
@article{arxiv.1312.2660,
title = {Thermodynamic Study of Nodal Structure and Multiband Superconductivity of KFe2As2},
author = {Shunichiro Kittaka and Yuya Aoki and Naoki Kase and Toshiro Sakakibara and Taku Saito and Hideto Fukazawa and Yoh Kohori and Kunihiro Kihou and Chul-Ho Lee and Akira Iyo and Hiroshi Eisaki and Kazuhiko Deguchi and Noriaki K. Sato and Yasumasa Tsutsumi and Kazushige Machida},
journal= {arXiv preprint arXiv:1312.2660},
year = {2013}
}
Comments
4 pages, 4 figures, published in J. Phys. Soc. Jpn