Effect of hydrostatic pressure on superconductivity of MgB2

The effect of hydrostatic pressure on superconductivity of hexagonal bulk MgB2 was investigated using the first-principles calculations. The calculations were performed based on the density functional theory employing the very recently developed EPW code incorporated in Quantum ESPRESSO computational package. The phonon density of states (PhDOS), isotropic Eliashberg function α2F(ω), the superconducting gap along real and imaginary frequency axes, the electron-phonon coupling constant λ, and the superconducting critical temperature Tc were computed within the general framework of Eliashberg formalism. The results show that hydrostatic pressure enhances superconductivity of the material. At equilibrium, where the hydrostatic pressure of the system is almost zero, the calculated Tc value is 35.67 K. It is relatively nearer to the experimental value of 39 K. The slight underestimation is attributed to the LDA-DFT approximation employed. This value is enhanced to around 95 K at hydrostatic pressure of 6500 kbar and then starts to decrease slowly. We emphasize that our approach to lattice strain engineering, with the target of enhancing Tc as demonstrated in this work, can be applied to various strain-engineering problems in other functional materials.