Strong nodeless pairing on separate electron Fermi surface sheets in (Tl, K)Fe${}_{1.78}$Se${}_2$ probed by ARPES

Abstract

We performed a high-resolution angle-resolved photoemission spectroscopy study of the Tl${}_{0.63}$K${}_{0.37}$Fe${}_{1.78}$Se${}_2$ superconductor ($T_c=29$ K). We show the existence of two electronlike bands at the M$(\pi ,0)$ point which cross the Fermi level at similar Fermi wave vectors to form nearly circular electronlike Fermi surface pockets. We observe a nearly isotropic $\sim$ 8.5 meV superconducting gap ($\Delta /k_B{T}_c\sim 7$) on these Fermi surfaces. Our analysis of the band structure around the Brillouin zone centre reveals two additional electronlike Fermi surfaces: a very small one and a larger one with $k_F$ comparable to the FS pockets at M. Interestingly, a SC gap with a magnitude of $\sim$ 8 meV also develops along the latter FS. Our observations are consistent with the s-wave strong coupling scenario.

5 pages, 4 figures

References in corpus (5)

• Observation of Fermi-surface-dependent nodeless superconducting gaps in Ba0.6K0.4Fe2As2
• Superconducting gap symmetry of Ba0.6K0.4Fe2As2 studied by angle-resolved photoemission spectroscopy
• Multiple Nodeless Superconducting Gaps in (Ba0.6K0.4)Fe2As2 Superconductor from Angle-Resolved Photoemission Spectroscopy
• Momentum-dependence of Superconducting Gap, strong-coupling dispersion Kink, and tightly bound Cooper pairs in the high-Tc (Sr,Ba)1-x(K,Na)xFe2As2 superconductors
• Electronic structure of heavily electron-doped BaFe${}_{1.7}$Co${}_{0.3}$As${}_2$ studied by angle-resolved photoemission

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• Superconductivity and normal state properties of single-crystalline Tl0.47Rb0.34Fe1.63Se2 as seen via 77Se and 87Rb NMR