Study on the relationship between uniaxial strain and critical transition temperature of MgB₂based on...

It has been indicated the critical transition temperature (T_c) of MgB₂decreases with the increase of hydrostatic pressure, but this is a comprehensiveT_cchange after the multiaxial strain, and the influence of strain onT_cis not fully understood. In this paper, based on the McMillan superconducting calculation formula and the first-principles density functional theory, theT_cchange and the properties of MgB₂such as energy band, Fermi surface, differential charge density, and phonon dispersion under uniaxial strain were studied, and the relationship between uniaxial strain and these properties was analyzed. The calculatedT_cof MgB₂at zero strain was 38.35 K, which is in good agreement with the experimental value of 39 K. When thea-axis strain was 1%, theT_cvalue could increase to 49.7 K, and there was a further improvement trend. When thea-axis compression strain was -1%,T_cdecreases to 31.52 K. When thec-axis tension-compression strain was applied, the change ofT_cvalue was small. Further analysis showed that the impact ofa-axis strain on the differential charge density, electronic band structure, phonon dispersion, and other properties of MgB₂was significantly greater than that ofc-axis strain, and the influence of these properties onT_cwas discussed. The work in this paper has certain theoretical and guiding significance for preparing MgB₂with higherT_cand the study of the effect of uniaxial strain onT_cof superconducting materials.