Vortex matter freezing in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ samples with a very dense distribution of columnar defects

TL;DR

This paper investigates how vortex structures in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ with dense columnar defects freeze into liquid-like configurations, proposing a relaxation model based on double-kink excitations and distinguishing these states from equilibrium Bose-glass phases.

Contribution

The study introduces a relaxation model for vortex freezing driven by double-kink excitations and characterizes the resulting non-equilibrium vortex states in dense defect environments.

Findings

Vortex structures freeze into liquid-like states at low fields.

The relaxation barrier and freezing temperature are estimated.

Frozen vortex states are out-of-equilibrium, non-entangled liquids.

Abstract

We show that the dynamical freezing of vortex structures nucleated at diluted densities in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ samples with a dense distribution of columnar defects, $B \sim 10^{-2} B_{\Phi}$ with $B_{\Phi}=5$\,kG, results in configurations with liquid-like correlations. We propose a freezing model considering a relaxation dynamics dominated by double-kink excitations driven by the local stresses obtained directly from experimental images. With this model we estimate the relaxation barrier and the freezing temperature. We argue that the low-field frozen vortex structures nucleated in a dense distribution of columnar defects thus correspond to an out-of-equilibrium non-entangled liquid with strongly reduced mobility rather than to a snapshot of a metastable state with divergent activation barriers as for instance expected for the Bose-glass phase at equilibrium.