Pressure Effects and Large Polarons in Layered MgB2 Superconductor
Abstract
We consider the dependence of the MgB2 superconducting critical temperature on the pressure. Our model exploits the influence of the large polarons on the band structure of the layered MgB2 superconductor. Namely, the hole Pekar-Froehlich polarons form quasi two-dimensional potential wells in the boron plane which shift the positions of the sigma- and pi-bands. This energy shift depends on the pressure and the Cooper pairing of the correlated sigma-electrons happens inside polaron wells. The results obtained are as follows: dTc/dp = -α (5.2 0.9) K/GPa or dTc/dp = -α (6.9 1.1) K/GPa for a different choice of the Grueneisen parameter. Being compared with known experimental data they give us a resonable interval for the value of the Froehlich electron-phonon coupling constant: α = 0.15 - 0.45.
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