Friedel Oscillations as a Probe of Fermionic Quasiparticles

TL;DR

This paper investigates how Friedel oscillations, caused by impurities in electron systems, can reveal properties of fermionic quasiparticles in strongly correlated materials like cuprate superconductors, considering complex factors beyond simple models.

Contribution

It provides a detailed analysis of Friedel oscillations in realistic materials, incorporating band structure, quasiparticle lifetime, and superconducting gaps, with experimental comparisons.

Findings

Friedel oscillations are sensitive to quasiparticle properties.

Experimental data shows interplay between chemical potential and pairing gap.

Analysis helps probe fermionic excitations in correlated materials.

Abstract

When immersed in a see of cold electrons, local impurities give rise to density modulations known as Friedel oscillations. In spite of the generality of this phenomenon, the exact shape of these modulations is usually computed only for non-interacting electrons with a quadratic dispersion relation. In actual materials, one needs to take into account several additional factors, such as (i) the details of the band structure, (ii) the lifetime of quasiparticles, (iii) in superconductors, the presence of a pairing gap. Studying how these effects influence Friedel oscillations is a viable way to access the properties of fermionic excitations in strongly-correlated materials. In this work we analyze the signatures of Friedel oscillations in STM and X-ray scattering experiments, focusing on the concrete example of cuprates superconductors. A detailed comparison with recent experiments reveals a rich interplay between local modulation of the chemical potential and of the pairing gap.