Melting of 'porous' vortex matter

TL;DR

This paper investigates the melting behavior of a 'porous' vortex matter in irradiated superconductors, revealing a first-order melting of crystallites within a solid matrix and a transition to continuous melting influenced by defect density.

Contribution

It introduces the concept of 'porous' vortex matter with embedded vortex crystallites and characterizes its melting transition, including the effects of defect density and temperature.

Findings

Crystallites melt via a first-order transition while the matrix remains solid.

Melting temperature increases with columnar defect density.

A sharp kink indicates a transition from crystallite to matrix melting.

Abstract

Bitter decoration and magneto-optical studies reveal that in heavy-ion irradiated superconductors, a 'porous' vortex matter is formed when vortices outnumber columnar defects (CDs). In this state ordered vortex crystallites are embedded in the 'pores' of a rigid matrix of vortices pinned on CDs. The crystallites melt through a first-order transition while the matrix remains solid. The melting temperature increases with density of CDs and eventually turns into a continuous transition. At high temperatures a sharp kink in the melting line is found, signaling an abrupt change from crystallite melting to melting of the rigid matrix.