Optimum pinning of the vortex lattice in extremely type-II layered superconductors

Abstract

The two-dimensional ͑2D͒ vortex lattice in the extreme type-II limit is studied by Monte Carlo simulation of the corresponding 2D Coulomb gas, with identical pins placed at sites coinciding with the zero-temperature triangular vortex lattice. At weak pinning we find evidence for 2D melting into an intermediate hexatic phase. The strong pinning regime shows a Kosterlitz-Thouless transition, driven by interstitial vortex/antivortex excitations. A stack of such identical layers with a weak Josephson coupling models a layered superconductor with a triangular arrangement of columnar pins at the matching field. A partial duality analysis finds that layer decoupling of the flux-line lattice does not occur at weak pinning for temperatures below 2D melting.

Collective pinning of the vortex lattice by columnar defects in layered superconductors

“…Indeed, the above perturbative result for the phase auto-correlation function across layers indicates that the Bose-glass melting transition occurs at a field approximtely e times smaller than the 2D-3D cross-over field (17), in which case the argument raised to the power n on the right-hand side of Eq. (16) is set to unity instead.…”

“…Macroscopic phase coherence is monitored by the two-dimensional (2D) phase rigidity given by one over the dielectric constant of the 2D Coulomb gas ensemble [17] that corresponds to the frustrated XY model (2). Vortex/anti-vortex excitations not associated with displacements of the zero-temperature vortex lattice are suppressed exponentially at temperatures far below the Kosterlitz-Thouless transition.…”

“…Also above, N vx denotes the total number of vortices, while a vx = a/f 1/2 . Finally, J 0 denotes the gaussian phase rigidity [17]. Generalized phase auto-correlation functions…”

Defective vortex lattices in layered superconductors with point pins at the extreme type-II limit

“…Coulomb gas ensemble with pins that describes the vortex degrees of freedom on the dual square lattice [8]. The ensemble for each layer l is weighted by the Boltzmann distribution set by the energy functional…”

“…The former is achieved through bulk pinning [8], and the latter then follows under periodic boundary conditions. Consider now a single unbound dislocation with Burgers vector b that slides along it glide plane [1] a distance δR df with respect to its location at zero temperature.…”