Carbon-substitution dependent multiple superconducting gap of MgB$_{2}$: a "sub-meV" resolution photoemission study

TL;DR

This study uses sub-meV resolution photoemission spectroscopy to investigate how carbon substitution affects the multiple superconducting gaps in MgB₂, revealing distinct behaviors of the σ and π gaps with doping.

Contribution

It provides detailed experimental insights into the doping dependence of multiple superconducting gaps in MgB₂ using high-resolution photoemission spectroscopy.

Findings

σ gap decreases proportionally with Tc

π gap remains nearly unchanged with doping

Two-band theory explains the observed gap behaviors

Abstract

``Sub-meV'' resolution photoemission spectroscopy was used to study carbon-substitution dependence on the multiple superconducting gap of Mg(B$_{1 - x}$C$_{x})_{2}$. Two features corresponding to $\sigma $ and $\pi $ gaps are clearly observed in the raw spectra up to carbon concentration x = 7.5 {%}. The observed x dependence of the two gaps shows a qualitatively different behavior: a marked change of the $\sigma $ gap proportional to the $T_{c}$ variation and a negligible one of the $\pi $ gap. This as well as the temperature dependence can be explained with the two-band mean-field theory. Implications from the present study are discussed.