Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 3: Superconductivity: Properties and Electronic Structure I

TT 3.7: Vortrag

Montag, 12. März 2018, 11:00–11:15, H 0110

Strain-enhanced three-gap superconductivity in monolayer MgB₂ — •Alex Aperis¹, Jonas Bekaert², Bart Partoens², Milorad V. Milošević², and Peter M. Oppeneer¹ — ¹Uppsala University, Uppsala, Sweden — ²University of Antwerp, Antwerp, Belgium

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. Solving the anisotropic Eliashberg equations with ab initio calculated input for electrons, phonons and the electron-phonon coupling, 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 hybridise 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 T_c>50 K under biaxial tensile strain of ∼ 4 %, which is an enhancement that is stronger than in any other graphene-related superconductor known to date.