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تسجيل مستخدم جديدEvidence for a cos(4varphi) Modulation of the Superconducting Energy Gap of Optimally Doped FeTe_{0.6}Se_{0.4} Single Crystals Using Laser Angle-Resolved Photoemission Spectroscopy
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We study the superconducting(SC)-gap anisotropy of the Gamma-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(4varphi) 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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