Pinning of dynamic spin density wave fluctuations in the cuprate superconductors

TL;DR

This paper develops a theory explaining how local imperfections in d-wave superconductors pin dynamic spin density wave fluctuations, resulting in static modulations observable via STM, while SDW correlations stay dynamic, linking to neutron scattering data.

Contribution

It introduces a novel theoretical framework for understanding the pinning of dynamic SDW fluctuations by impurities in cuprate superconductors.

Findings

Static spatial modulations in spin observables due to pinning

Connection between STM modulations and neutron scattering spectra

SDW correlations remain dynamic despite static modulations

Abstract

We present a theory of the pinning of dynamic spin density wave (SDW) fluctuations in a d-wave superconductor by local imperfections which preserve spin-rotation invariance, such as impurities or vortex cores. The pinning leads to static spatial modulations in spin-singlet observables, while the SDW correlations remain dynamic: these are the `Friedel oscillations' of a spin-gap antiferromagnet. We connect the spectrum of these modulations as observed by scanning tunnelling microscopy to the dynamic spin structure factor measured by inelastic neutron scattering.