A weak-coupling superconductivity in the electron doped NaFe$_{0.95}$Co$_{0.05}$As is revealed by ARPES

TL;DR

This study uses ARPES to reveal weak-coupling superconductivity in electron-doped NaFe$_{0.95}$Co$_{0.05}$As, showing isotropic gaps and no pseudogaps, with gap behavior following BCS theory.

Contribution

First systematic ARPES investigation of electronic structure and superconducting gaps in this specific electron-doped iron pnictide.

Findings

Weak-coupling superconductivity indicated by Δ/K_B T_c range of 1.8-2.1

Absence of pseudogaps above T_c

Superconducting gaps are nearly isotropic along k_z

Abstract

We report a systematic study on the electronic structure and superconducting (SC) gaps in electron doped NaFe$_{0.95}$Co$_{0.05}$As superconductor using angle-resolved photoemission spectroscopy. Hole-like Fermi sheets are at the zone center and electron-like Fermi sheets are at the zone corner, and are mainly contributed by $xz$ and $yz$ orbital characters. Our results reveal a $\frac{\Delta}{K_B T_c}$ in the range of 1.8-2.1, suggesting a weak-coupling superconductivity in these compounds. Gap closing above the transition temperature ($T_c$) shows the absence of pseudogaps. Gap evolution with temperature follow the BCS gap equation near the $\Gamma$, $Z$, and $M$ high symmetry points. Furthermore, an almost isotropic superconductivity along $k_z$ direction in the momentum space is observed by varying the excitation energies.