Superconductivity and topological properties of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>MgB</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>-type diborides from first principles
Yipeng An, Jie Li, Kun Wang, Guangtao Wang, Shijing Gong, Chunlan Ma, Tianxing Wang, Zhaoyong Jiao, Xiao Dong, Guoliang Xu, Ruqian Wu, Wu-Ming Liu
Abstract
The superconductivities and topological properties of ${\mathrm{MgB}}_{2}$-type diborides are investigated by means of first-principles calculations with different exchange-correlation functionals. Functionals with the van der Waals (vdW) correction (such as OptB88-vdW) may predict critical temperature (${T}_{c}$) comparable with experimental results for several ${\mathrm{MgB}}_{2}$-type superconductors, particularly for the pristine ${\mathrm{MgB}}_{2}$ (39.3 vs 39 K). Interestingly, the spin-fluctuation is found to play a significant role in the superconducting behavior of diborides with transition metal elements, and their ${T}_{c}$ can be enhanced monotonically by applying tensile strains. Furthermore, Dirac surface states of $\mathrm{Ta}\phantom{\rule{0.16em}{0ex}}{\mathrm{B}}_{2}$ and ${\mathrm{NbB}}_{2}$ are revealed, suggesting their potential use as topological superconducting materials. This paper provides a useful guideline for ab initio studies of superconductivities and topological properties of vdW layered materials.