Vortex dynamics and states of artificially layered superconducting films with correlated defects

TL;DR

This study investigates vortex dynamics and phase transitions in multilayered superconducting films with correlated defects, revealing complex vortex phases and deviations from theoretical models.

Contribution

It provides new insights into vortex phases, dimensional crossover, and glass exponents in layered superconductors with correlated defects.

Findings

Identification of multiple vortex phases including 2D and 3D behaviors

Observation of a second order phase transition from vortex liquid to glass

Distinctive temperature and field dependence of the glass exponent μ

Abstract

Linear resistances and $IV$-characteristics have been measured over a wide range in the parameter space of the mixed phase of multilayered a-TaGe/Ge films. Three films with varying interlayer coupling and correlated defects oriented at an angle $\approx 25$ from the film normal were investigated. Experimental data were analyzed within vortex glass models and a second order phase transition from a resistive vortex liquid to a pinned glass phase. Various vortex phases including changes from three to two dimensional behavior depending on anisotropy have been identified. Careful analysis of $IV$-characteristics in the glass phases revealed a distinctive $T$ and $H$-dependence of the glass exponent $\mu$. The vortex dynamics in the Bose-glass phase does not follow the predicted behavior for excitations of vortex kinks or loops.