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arXiv · 1312.2660

Thermodynamic Study of Nodal Structure and Multiband Superconductivity of KFe2As2

Shunichiro Kittaka·Yuya Aoki·Naoki Kase·Toshiro Sakakibara·Taku Saito·Hideto Fukazawa·Yoh Kohori·Kunihiro Kihou·Chul-Ho Lee·Akira Iyo·Hiroshi Eisaki·Kazuhiko Deguchi·Noriaki K. Sato·Yasumasa Tsutsumi·Kazushige Machida
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Abstract

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 $\sqrt{H}$ 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.

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Shunichiro Kittaka, Yuya Aoki, Naoki Kase, Toshiro Sakakibara, Taku Saito, Hideto Fukazawa, Yoh Kohori, Kunihiro Kihou, Chul-Ho Lee, Akira Iyo, Hiroshi Eisaki, Kazuhiko Deguchi, Noriaki K. Sato, Yasumasa Tsutsumi, Kazushige Machida. 2013-12-10. Thermodynamic Study of Nodal Structure and Multiband Superconductivity of KFe2As2. https://doi.org/10.7566/jpsj.83.013704

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