AlB2 and MgB2: a comparative study of their electronic, phonon and superconductivity properties via first principles

Recently, the AlB2-type compounds (such as AlB2 and MgB2) which exhibit Dirac Nodal Line (DNLs) semimetal on their electronic band structure and Phononic Weyl Nodal Straight Lines (PTWNLs) on their phonon spectrum, have received wide attentions on their novel properties. Up to date, no comparative studies have been investigated on their electronic structures, phonon spectrum, and electron phonon coupling (EPC) under the conditions of carrier doping and strain engineering. Here, we systemically investigate their above properties under carrier doping and strain engineering by first-principles calculations. The results show that the superconducting transition temperature Tc can be enhanced by electron doping and tensile strain. For AlB2, the tensile strain of 6% can enhance Tc to 10.25 K and with the doping concentrate of 0.1 e- per cell can enhance Tc reach to 9.89 K. Moreover, the physical quantities related to superconductivity of AlB2 are more affected by carrier doping than MgB2. Our results provide a theoretical reference to explore the correlation between electronic and phonon topological properties in AlB2-type materials.