Searching for higher superconducting transition temperature in strained MgB2 using first principles calculations

Since the discovery of the amazing high superconducting transition temperature (T$_{c})$ in non-oxide MgB$_{2}$, great efforts have been made on the search for higher T$_{c}$ in MgB$_{2}$ and related materials by either chemical substitutions or by applying pressures to modify the lattice of MgB$_{2}$. Little success has been achieved so far due to the fact that the T$_{c}$ is always suppressed using either method. To tailor the T$_{c}$ in MgB$_{2}$, the full atomic-level understanding of underlying mechanism of chemical and lattice effects is required. According to the McMillan-Allen-Dynes analysis, T$_{c}$ in MgB$_{2}$ is controlled by the collective contributions from phonon frequency, electron-phonon coupling and Coulomb repulsion. Consideration of one single parameter alone cannot guarantee the improvement of T$_{c}$ because of the strong coupling and competing of other parameters. Here we present a detailed first-principles density functional analysis of the effects of lattice strains to superconducting properties of MgB$_{2.}$ On the basis of our results for structural, electronic, vibrational and superconducting properties of strained MgB$_{2}$, we show how higher superconducting transition temperature might be achieved in strained MgB$_{2}$ superconductor.