Evolution of multi-gap superconductivity in the atomically thin limit: Strain-enhanced three-gap superconductivity in monolayer MgB₂

2017/08/14 by J. Bekaert, A. Aperis, B. Partoens +2 · 1 citation
Physics and Astronomy · #cond-mat.supr-con

paper · pdf · doi:10.1103/physrevb.96.094510

published as Phys. Rev. B 96, 094510 (2017) · To appear in Phys. Rev

arxiv created 2017/08/14 · arxiv updated 2017/09/20

Abstract

Starting from first principles, we show the formation and evolution of superconducting gaps in MgB₂ at its ultrathin limit. Atomically thin MgB₂ is distinctly different from bulk MgB₂ in that surface states become comparable in electronic density to the bulk-like σ- and π-bands. Combining the ab initio electron-phonon coupling with the anisotropic Eliashberg equations, we show that monolayer MgB₂ develops three distinct superconducting gaps, on completely separate parts of the Fermi surface due to the emergent surface contribution. These gaps hybridize nontrivially with every extra monolayer added to the film, owing to the opening of additional coupling channels. Furthermore, we reveal that the three-gap superconductivity in monolayer MgB₂ is robust over the entire temperature range that stretches up to a considerably high critical temperature of 20 K. The latter can be boosted to >50 K under biaxial tensile strain of ∼ 4%, which is an enhancement stronger than in any other graphene-related superconductor known to date.

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