Evidence for a cos(4φ) Modulation of the Superconducting Energy Gap of Optimally Doped FeTe_{0.6}Se_{0.4} Single Crystals Using Laser Angle-Resolved Photoemission Spectroscopy

K. Okazaki; Y. Ito; Y. Ota; Y. Kotani; T. Shimojima; T. Kiss; S. Watanabe; C. -T. Chen; S. Niitaka; T. Hanaguri; H. Takagi; A. Chainani; S. Shin

doi:10.1103/physrevlett.109.237011

arXiv · 1207.6571

Evidence for a cos(4φ) Modulation of the Superconducting Energy Gap of Optimally Doped FeTe_{0.6}Se_{0.4} Single Crystals Using Laser Angle-Resolved Photoemission Spectroscopy

K. Okazaki·Y. Ito·Y. Ota·Y. Kotani·T. Shimojima·T. Kiss·S. Watanabe·C. -T. Chen·S. Niitaka·T. Hanaguri·H. Takagi·A. Chainani·S. Shin

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Abstract

We study the superconducting(SC)-gap anisotropy of the Γ-centered hole Fermi surface in optimally doped FeTe_{0.6}Se_{0.4} (T_c = 14.5 K), using laser-excited angle-resolved photoemission spectroscopy (ARPES). We observe sharp superconducting coherence peaks at T = 2.5 K. In contrast to earlier ARPES studies but consistent with thermodynamic results, the momentum dependence shows a \cos(4φ) modulation of the SC-gap anisotropy. The observed SC-gap anisotropy strongly indicates that the pairing interaction is not a conventional phonon-mediated isotropic one. Instead, the results suggest the importance of second-nearest-neighbor electronic interactions between the iron sites in the framework of s_\pm-wave superconductivity.

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K. Okazaki, Y. Ito, Y. Ota, Y. Kotani, T. Shimojima, T. Kiss, S. Watanabe, C. -T. Chen, S. Niitaka, T. Hanaguri, H. Takagi, A. Chainani, S. Shin. 2012-12-10. Evidence for a cos(4φ) Modulation of the Superconducting Energy Gap of Optimally Doped FeTe_{0.6}Se_{0.4} Single Crystals Using Laser Angle-Resolved Photoemission Spectroscopy. https://doi.org/10.1103/physrevlett.109.237011

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