Vortex Solid-Liquid Transition in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ with a High Density of Strong Pins

TL;DR

This study investigates the vortex solid-liquid transition in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ with high-density columnar defects, revealing that such defects do not enhance the irreversibility line at low vortex densities and characterizing the vortex Bose glass phase.

Contribution

It provides new insights into vortex matter behavior in high-temperature superconductors with dense columnar defects, especially regarding phase correlations and transition mechanisms.

Findings

Irreversibility line not increased by defects at low vortex densities

Vortex positional correlations are smaller in the Bose glass than in low-field vortex solid

Bose-glass-to-liquid transition involves rapid loss of c-axis phase coherence

Abstract

The introduction of a large density of columnar defects in %underdoped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ crystals does not, at sufficiently low vortex densities, increase the irreversibility line beyond the first order transition (FOT) field of pristine crystals. At such low fields, the flux line wandering length $r_{w}$ behaves as in pristine %Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ crystals. Next, vortex positional correlations along the $c$--axis in the vortex Bose glass at fields above the FOT are smaller than in the low--field vortex solid. Third, the Bose-glass-to-vortex liquid transition is signaled by a rapid decrease in c-axis phase correlations. These observations are understood in terms of the ``discrete superconductor'' model.