Tuning the electronic properties of MgB2by substitution with Mn and C

Abstract

We use high-resolution angle-resolved photoemission spectroscopy (ARPES) to investigate the electronic band structure of the superconductors Mg_0.995Mn_0.005B₂and Mg(B_0.98C_0.02)₂, in comparison with pristine MgB₂. Our experimental findings reveal modest changes in the size of the Fermi surface sheets following manganese or carbon substitution, with the most pronounced effect observed in the outermostσband. Additionally, the dispersion kink, indicative of strong renormalization due to the interaction between conduction electrons and phonon modes near -0.065 eV, remains unaffected by chemical substitution. Given that the superconducting transition temperature decreases significantly more rapidly in Mn-substituted MgB₂than in C-substituted MgB₂, our ARPES results strongly suggest that the primary mechanism behind the pronouncedTCsuppression in Mn-MgB₂is the disruption of Cooper pairs via Abrikosov-Gorkov spin-flip scattering caused by the local magnetic moments of Mn.

Keywords: ARPES; MgB2; electronic structure; superconductivity.