Genuine Electronic Structure and Superconducting Gap Structure in (Ba$_{0.6}$K$_{0.4}$)Fe$_{2}$As$_{2}$ Superconductor

Yongqing Cai; Jianwei Huang; Taimin Miao; Dingsong Wu; Qiang Gao; Cong Li; Yu Xu; Junjie Jia; Qingyan Wang; Yuan Huang; Guodong Liu; Fengfeng Zhang; Shenjin Zhang; Feng Yang; Zhimin Wang; Qinjun Peng; Zuyan Xu; Lin Zhao; X. J. Zhou

doi:10.1016/j.scib.2021.05.015

paper

Genuine Electronic Structure and Superconducting Gap Structure in (Ba $_{0.6}$ K $_{0.4}$ )Fe $_{2}$ As $_{2}$ Superconductor

arXiv:2104.01407 · doi:10.1016/j.scib.2021.05.015

Abstract

The electronic structure and superconducting gap structure are prerequisites to establish microscopic theories in understanding the superconductivity mechanism of iron-based superconductors. However, even for the most extensively studied optimally-doped (Ba $_{0.6}$ K $_{0.4}$ )Fe $_{2}$ As $_{2}$ , there remain outstanding controversies on its electronic structure and superconducting gap structure. Here we resolve these issues by carrying out high-resolution angle-resolved photoemission spectroscopy (ARPES) measurements on the optimally-doped (Ba $_{0.6}$ K $_{0.4}$ )Fe $_{2}$ As $_{2}$ superconductor using both Helium lamp and laser light sources. Our results indicate the "flat band" feature observed around the Brillouin zone center in the superconducting state originates from the combined effect of the superconductivity-induced band back-bending and the folding of a band from the zone corner to the center. We found direct evidence of the band folding between the zone corner and the center in both the normal and superconducting state. Our resolution of the origin of the flat band makes it possible to assign the three hole-like bands around the zone center and determine their superconducting gap correctly. Around the zone corner, we observe a tiny electron-like band and an M-shaped band simultaneously in both the normal and superconducting states. The obtained gap size for the bands around the zone corner ( $\sim$ 5.5 meV) is significantly smaller than all the previous ARPES measurements. Our results establish a new superconducting gap structure around the zone corner and resolve a number of prominent controversies concerning the electronic structure and superconducting gap structure in the optimally-doped (Ba $_{0.6}$ K $_{0.4}$ )Fe $_{2}$ As $_{2}$ . They provide new insights in examining and establishing theories in understanding superconductivity mechanism in iron-based superconductors.

arXiv comment26 Pages, 7 figures

Genuine Electronic Structure and Superconducting Gap Structure in (Ba $_{0.6}$ K $_{0.4}$ )Fe $_{2}$ As $_{2}$ Superconductor

Abstract

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Genuine Electronic Structure and Superconducting Gap Structure in (Ba0.6​K0.4​)Fe2​As2​ Superconductor

Abstract

References in corpus (31)

Cited by in corpus (4)

Genuine Electronic Structure and Superconducting Gap Structure in (Ba $_{0.6}$ K $_{0.4}$ )Fe $_{2}$ As $_{2}$ Superconductor