Disorder-Driven Magnetic Field Dependence of the Internal Field Distribution in the Bragg Glass Phase of Type-II Superconductors

We use the replica variational method to study the effects of weak point disorder on the variance of the internal field distribution measured in NMR and muon-spin rotation experiments in type-II superconductors. We show that for a simple model there is significant magnetic field dependence which is extrinsic and disorder-driven, and does not have a microscopic (non $s-$wave pairing) origin. Results are presented where we examine the dependence of the magnetic field variance upon the strength of the applied external field.