Magnetic field dependence of the electrical conductivity in V3Ge in the vicinity of Hc2

TL;DR

This paper investigates the magnetic field dependence of electrical conductivity in V3Ge near Hc2, revealing a narrow transition into the Abrikosov vortex state that may be first-order and independent of superconducting pair density.

Contribution

It demonstrates that the vortex lattice melting transition in V3Ge is very narrow and can be observed below Hc2, challenging previous assumptions about its nature.

Findings

Transition into vortex state is very narrow in high-quality samples.

The transition can be first-order and occurs below Hc2.

Vortex lattice melting observed before high-Tc superconductor discovery.

Abstract

The phase transition from the Abrikosov state to the normal state with superconducting fluctuations observed below the second critical field and well-known as vortex lattice melting was one of the most popular problems in the nineties. This problem had became popular after the discovery of high-Tc superconductors because the fluctuation phenomena are much stronger in the HTSC than in the conventional superconductors. Most people are sure that this sharp transition was observed for the present only in HTSC and are ignorant that it was observed as far back as 1981, before the HTSC discovery. In the last years some papers devoted to the problem of vortex lattice melting in conventional superconductors were published. The authors of these papers and others should be aware of the result obtained before the HTSC discovery. It was found first in the presented paper that the transition into the Abrikosov vortex state is very narrow in high quality samples with weak pinning and it is observed below the second critical field. These results signify that this phase transition can be first-order and it is not connected directly with appearance of a finite density of superconducting pairs.