Multiple Changes of Order of the Vortex Melting Transition in BSCCO with Dilute Columnar Defects

TL;DR

This study investigates how dilute columnar defects in BSCCO crystals cause multiple changes in the vortex melting transition order, revealing complex phase behavior with critical points and a second-order transition region.

Contribution

It demonstrates the transformation of vortex lattice melting behavior due to dilute columnar defects and maps the phase transitions down to low temperatures using the shaking technique.

Findings

First-order vortex melting line becomes segmented with alternating transition types.

Critical points shift with defect density, expanding the second-order transition region.

A low temperature critical point was observed in one sample.

Abstract

A low concentration of columnar defects is reported to transform a first-order vortex lattice melting line in BSCCO crystals into alternating segments of first-order and second-order transitions separated by two critical points. As the density of CDs is increased, the critical points shift apart and the range of the intermediate second-order transition expands. A third, low temperature critical point was also observed in one sample. The measurement of equilibrium magnetization and the mapping of the melting line down to 27K was made possible by employment of the shaking technique.