Superconducting-Gap Anisotropy of Iron Pnictides Investigated via Combinatorial Microwave Measurements

Tatsunori Okada; Yoshinori Imai; Kentaro Kitagawa; Kazuyuki Matsubayashi; Masamichi Nakajima; Akira Iyo; Yoshiya Uwatoko; Hiroshi Eisaki; Atsutaka Maeda

doi:10.1038/s41598-020-63304-0

Superconducting-Gap Anisotropy of Iron Pnictides Investigated via Combinatorial Microwave Measurements

Sci Rep. 2020 Apr 27;10(1):7064. doi: 10.1038/s41598-020-63304-0.

Authors

Tatsunori Okada^{1

2}, Yoshinori Imai^{3

4}, Kentaro Kitagawa^{5

6}, Kazuyuki Matsubayashi^{5

7}, Masamichi Nakajima^{8

9}, Akira Iyo⁸, Yoshiya Uwatoko⁵, Hiroshi Eisaki⁸, Atsutaka Maeda¹⁰

Affiliations

¹ Department of Basic Science, University of Tokyo, Meguro, Tokyo, 153-8902, Japan. tatsu.okada@imr.tohoku.ac.jp.
² Institute for Materials Research, Tohoku University, Sendai, Miyagi, 980-8577, Japan. tatsu.okada@imr.tohoku.ac.jp.
³ Department of Basic Science, University of Tokyo, Meguro, Tokyo, 153-8902, Japan.
⁴ Department of Physics, Tohoku University, Sendai, Miyagi, 980-8578, Japan.
⁵ Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, 277-8581, Japan.
⁶ Department of Physics, University of Tokyo, Bunkyo, Tokyo, 113-0033, Japan.
⁷ Department of Engineering Science, University of Electro-Communications, Chofu, Tokyo, 182-8585, Japan.
⁸ National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, 305-8568, Japan.
⁹ Department of Physics, Osaka University, Toyonaka, Osaka, 560-0043, Japan.
¹⁰ Department of Basic Science, University of Tokyo, Meguro, Tokyo, 153-8902, Japan. cmaeda@mail.ecc.u-tokyo.ac.jp.

Abstract

One of the most significant issues for superconductivity is clarifying the momentum-dependent superconducting gap Δ([Formula: see text]), which is closely related to the pairing mechanism. To elucidate the gap structure, it is essential to investigate Δ([Formula: see text]) in as many different physical quantities as possible and to crosscheck the results obtained in different methods with each other. In this paper, we report a combinatorial investigation of the superfluid density and the flux-flow resistivity of iron-pnictide superconductors; LiFeAs and BaFe₂(As_1-xP_x)₂ (x = 0.3, 0.45). We evaluated Δ([Formula: see text]) by fitting these two-independent quantities with a two-band model simultaneously. The obtained Δ([Formula: see text]) are consistent with the results observed in angle-resolved photoemission spectroscopy (ARPES) and scanning-tunneling spectroscopy (STS) studies. We believe our approach is a powerful method for investigating Δ([Formula: see text]) because it does not require a sample with clean surface unlike ARPES and STS experiments, or a rotational magnetic-field system for direct measurements of the angular dependence of thermodynamic quantities.