Estimates for the thermodynamic signatures of vortex-lattice melting in conventional superconductors

► The melting theory for the vortex lattice is reviewed. ► The vortex lattice melting lines for common non-cuprate superconductors are determined. ► Discontinuities in magnetization and entropy are predicted and found to be measurable. ► Comparisons are made with recent measurements. The first-order nature of the vortex-lattice melting transition in copper-based layered high-Tc superconductors is well established. The associated discontinuities in magnetization have been extensively studied, for example, in YBa2Cu3O7[1,2] and Bi2Sr2CaCu2O8[3], while the respective latent heats have been systematically investigated only in YBa2Cu3O7 and related compounds [4–13]. The apparent absence of such signatures in conventional superconductors such as Nb raises the question whether or not the concept of vortex-lattice melting is applicable at all in such materials [14]. Based on available literature to describe the vortex-state and using the Lindemann criterion, we estimate quantitatively the order of magnitude for the expected latent heats of melting and the associated discontinuities in magnetization, respectively, as functions of a few known material parameters. It turns out that both thermodynamic quantities are not strictly vanishing even in isotropic materials as long as κ>1/2, but they are small and may often be beyond the available experimental resolution.