Mishonov Group

An explicit expression for the temperature dependence of the specific heat of clean anisotropic-gap superconductors is derived within the weak-coupling BCS approximation. The specific heat is presented as a functional of the superconducting gap on the Fermi surface. The obtained formula interpolates between the correct low coupling jump at Tc and the low-temperature behavior for T<<Tc. For isotropic superconductors, the formula gives a relation between the specific heat and the superconducting gap. For anisotropic superconductors, the interpolation formula incorporates averaging of powers of the gap anisotropy function over the Fermi surface and provides a suitable set for fitting model Hamiltonians to experimental data. The work of the interpolation formula is illustrated by (i) the Pokrovsky formula for the specific heat jump; (ii) Gor'kov and Melik-Barkhudarov formulas for the Ginzburg-Landau coefficients; (iii) the Moskalenko two-band formula for the specific heat jump; (iv) the temperature dependence of the specific heat for the two-band model, applicable to MgB2; (v) the two-dimensional d-wave model, applicable for YBa2Cu3O7–delta; and (vi) the Zhitomirsky and Rice triplet p-wave model with horizontal line nodes for Sr2RuO4. The temperature dependence of the penetration depth is illustrated by fitting the general theoretical formula to the experimental data for MgB2, YBa2Cu3O7–delta, and the triplet superconductor Sr2RuO4.

Preprint: cond-mat/0212491

http://dx.doi.org/10.1103/PhysRevB.71.024520