Interactions, Distribution of Pinning Energies, and Transport in the Bose Glass Phase of Vortices in Superconductors

TL;DR

This paper investigates the ground state, energy distribution, and transport properties of vortices pinned to defects in superconductors, revealing how interactions influence vortex configurations and reduce transport via variable-range hopping in the Bose glass phase.

Contribution

It introduces a novel analysis of vortex configurations and energy distributions considering long-range interactions, using a Monte Carlo approach and an analogy with disordered semiconductors.

Findings

Strong correlations in vortex arrangements when London penetration depth exceeds fluxon spacing

Presence of a Coulomb gap in pinning energy distribution near the chemical potential

Reduction of vortex transport due to correlated pinning effects

Abstract

We study the ground state and low energy excitations of vortices pinned to columnar defects in superconductors, taking into account the long--range interaction between the fluxons. We consider the ``underfilled'' situation in the Bose glass phase, where each flux line is attached to one of the defects, while some pins remain unoccupied. By exploiting an analogy with disordered semiconductors, we calculate the spatial configurations in the ground state, as well as the distribution of pinning energies, using a zero--temperature Monte Carlo algorithm minimizing the total energy with respect to all possible one--vortex transfers. Intervortex repulsion leads to strong correlations whenever the London penetration depth exceeds the fluxon spacing. A pronounced peak appears in the static structure factor $S(q)$ for low filling fractions $f \leq 0.3$. Interactions lead to a broad Coulomb gap in the distribution of pinning energies $g(\epsilon)$ near the chemical potential $\mu$, separating the occupied and empty pins. The vanishing of $g(\epsilon)$ at $\mu$ leads to a considerable reduction of variable--range hopping vortex transport by correlated flux line pinning.