Superconducting gap anisotropy sensitive to nematic domains in FeSe

• DOI: 10.1038/s41467-017-02739-y
• Publication Date: 2018-01-12T16:00:20Z
• Authors: Takahiro Hashimoto; Yuichi Ota; Haruyoshi Q. Yama...; Yuya Suzuki; Takahiro Shimojima; Shuntaro Watanabe; Chuangtian Chen; Shigeru Kasahara; Yuji Matsuda; Takasada Shibauchi; Kozo Okazaki; Shik Shin
• Keywords: Orthorhombic crystal system

The structure of the superconducting gap in unconventional superconductors holds a key to understand momentum-dependent pairing interactions. In FeSe, there have been controversial results reporting nodal and nodeless structures, raising fundamental issue mechanisms iron-based superconductivity. Here, by utilizing polarization-dependent laser-excited angle-resolved photoemission spectroscopy, we report detailed momentum dependence single- multi-domain regions orthorhombic FeSe crystals. We confirm that has twofold in-plane anisotropy, associated with nematicity due orbital ordering. twinned regions, clearly find finite minima near vertices major axis elliptical zone-centered Fermi surface, indicating state. contrast, single-domain drops steeply zero narrow angle range, evidencing for nascent nodes. Such unusual node lifting can be explained nematicity-induced time-reversal symmetry breaking twin boundaries.