Weakly Pinned Bose Glass vs. Mott Insulator Phase in Superconductors

TL;DR

This paper investigates the transition between Mott insulator and Bose glass phases in irradiated superconductors, revealing how vortex interactions and material parameters influence phase properties and observable signatures.

Contribution

It demonstrates that repulsive vortex interactions eliminate the Mott insulator phase at the matching field and characterizes the weakly pinned Bose glass with a Coulomb gap.

Findings

Remnants of Mott insulator singularities persist for certain parameter ratios.

Weakly pinned Bose glass exhibits a soft Coulomb gap in pinning energy distribution.

Vortex interactions significantly alter phase behavior near the matching field.

Abstract

We study the properties of the Bose glass phase of localized flux lines in irradiated superconductors near the matching field $B_{\Phi}$. Repulsive vortex interactions destroy the Mott insulator phase predicted to occur at $B=B_\Phi$. For ratios of the penetration depth to average defect distance $\lambda / d \leq 1$ remnants of the Mott insulator singularities remain visible in the magnetization, the bulk modulus, and the magnetization relaxation, as B is varied near $B_{\Phi}$. For $\lambda \geq d$, the ensuing weakly pinned Bose glass is characterized by a soft Coulomb gap in the distribution of pinning energies.