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

TL;DR

This paper estimates the thermodynamic signatures of vortex-lattice melting in conventional superconductors, showing that such signatures are small but potentially detectable, extending the concept beyond high-Tc materials.

Contribution

It provides a quantitative estimation of latent heats and magnetization discontinuities in conventional superconductors using the Lindemann criterion.

Findings

Latent heats are small but non-zero in conventional superconductors.

Discontinuities in magnetization are present but often below experimental detection.

Vortex-lattice melting signatures are relevant for materials with ppa > 1/.

Abstract

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 and Bi2Sr2CaCu2O8, while the respective latent heats have been systematically investigated only in YBa2Cu3O7 and related compounds. 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. 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 $\kappa > 1/\sqrt{2}$, but they are small and may often be beyond the available experimental resolution.