Generalized joint density of states and its application to exploring the pairing symmetry of superconductors

TL;DR

This paper introduces a generalized joint density of states (GJDOS) incorporating coherence factors to analyze quasiparticle interference in superconductors, aiding in identifying pairing symmetries.

Contribution

The study develops GJDOS as a new tool linking local density of states and impurity response, revealing gap sign features and pairing symmetry in superconductors.

Findings

GJDOS matches QPI patterns in d-wave cuprates and iron-based superconductors.

GJDOS can identify sign changes in the superconducting gap.

Analytic and numerical results show strong agreement with experimental data.

Abstract

We introduce a generalized joint density of states (GJDOS), which incorporates the coherent factor into the JDOS, to study quasiparticle interference (QPI) in superconductors. The intimate relation between the Fourier-transformed local density of states and GJDOS is revealed: they corre- spond respectively to the real and imaginary parts of a generalized impurity-response function, and particularly share the same angular factors and singular boundaries, as seen from our approximate analytic results for d-wave superconductors. Remarkably, our numerical GJDOS analysis agrees well with the QPI patten of d-wave cuprates and s\pm-wave iron-based superconductors. Moreover, we illustrate that the present GJDOS scenario can uncover the sign features of the superconducting gap and thus can be used to explore the possible pairing symmetry of the KxFe2-ySe2 superconductors.