Anomalous vortex dynamics in 2D superconductors

Abstract

Low -frequency dynamic impedance ($σ^{-1}(ω,T)\equiv(σ_{1}+iσ_{2})^{-1}$) measurements on Josephson junction arrays with finite vortex screening length $ξ$, found that $σ_{1}\sim |\logω|$, $σ_{2}\sim$ constant. This implies anomalously sluggish vortex mobilities $μ_{V}(ω)\simσ_{1}^{-1}$, and is in conflict with general dynamical scaling expressions that yield, for low-$ω$, $σ_{1}\rightarrowξ^{2}$ and $σ_{2}\rightarrow 0$. We calculate : a) $σ(ω,T)$ by real-space vortex scaling; b) $μ_{V}(ω)$ using Mori's formalism for a screened Coulomb gas. We find, in addition to the usual critical (large-$ω$) and hydrodynamic (low-$ω$) regimes, a new intermediate-frequency scaling regime into which the experimental data fall. This resolves the above mentioned conflict and makes explicit predictions for the scaling form of $σ(ω,T)$, testable in SNS and SIS arrays.