Suppressed superconductivity in substrate-supported β12 borophene by tensile strain and electron doping

Planar borophene, the truly 2D monolayer boron, has been independently successfully grown on Ag(1 1 1) by two groups (2016 Nat. Chem. 8 563 and 2015 Science 350 1513), which has received widespreading attentions. The superconducting property has not been unambiguously observed, which is unexpected because light element boron should have strong electron-phonon coupling. To resolve this puzzle, we show that the superconducting transition temperature T-c of beta(12) borophene is effectively suppressed by the substrate-induced tensile strain and electron doping via first principles calculations. The biaxial tensile strain of 2% induced by Ag(1 1 1) significantly reduces Tc from 14 K to 2.95 K; electron doping of 0.1 e-per boron atom further shrinks Tc to 0.09 K. We also predict that the superconducting transition temperature in beta(12) can be enhanced to 22.82 K with proper compressive strain (-1%) and 18.97 K with hole doping (0.1 h(+) per boron). Further studies indicate that the variation of Tc is closely related to the density of states of s bands near the Fermi surface. Our results help to explain the challenges to experimentally probe superconductivity in substratesupported borophene.