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arXiv · 1101.4923

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

X. -P. Wang·T. Qian·P. Richard·P. Zhang·J. Dong·H. -D. Wang·C. -H. Dong·M. -H. Fang·H. Ding
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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$(π, 0)$ 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 ($Δ/k_BT_c\sim 7$) 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.

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X. -P. Wang, T. Qian, P. Richard, P. Zhang, J. Dong, H. -D. Wang, C. -H. Dong, M. -H. Fang, H. Ding. 2011-01-25. Strong nodeless pairing on separate electron Fermi surface sheets in (Tl, K)Fe$_{1.78}$Se$_2$ probed by ARPES. https://doi.org/10.1209/0295-5075%2F93%2F57001

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