High critical temperature and the resistive transition of MgB[sub 2

Abstract

We make a comparative study of MgB2 and cuprate high critical temperature superconductors. Unlike cuprates MgB2 shows typical behavior of phonon-mediated BCS superconductivity. The analytical expression for the so-called McMillan-Hopfield parameter implies that the l(l±1) hybridization of conduction band with high angular momentum l is beneficial for strong BCS superconductivity. The potential of further optimizing critical temperature is discussed in connection with the recent band structure calculations. The resistive transitions of high critical temperature cuprates and MgB2 near and below critical temperature are studied. A model R(T,H) equation fairly agrees with the experimental data of the untwined YBCO crystals as well as high critical temperature MgB2.