Strain Effect on the Superconductivity in Borophenes

The effects of strain on the structure stability, electron–phonon coupling (EPC), and superconductivity of two types of monolayer borophenes realized in the experiments are systematically investigated within the framework of density functional theory. We find that the electron–phonon coupling (EPC) in the buckled triangle borophene can be significantly enhanced by the suitable strain (−2–3%) due to the lower acoustic phonon branch softening. Our calculations suggest that a superconducting transition temperature (Tc) ranging from 24 to 32 K may be observed in the experiment. For the β12 borophene, the EPC constant (λ) and Tc exhibit a U-curve variation with the strain ranging from 0 to 12%. The highest Tc of 14.9 K can be obtained in the pristine structure. The stiffness of the lower acoustic phonon branches and the U-curve variation of N(EF) mainly from the pz electrons of boron are responsible for the change of the superconducting transition temperature with the increase of the tensile strain. Although borophenes have a highly anisotropic structure, the uniaxial strain effect on the superconductivity is isotropic.