Pair-breaking scattering interference as a mechanism for superconducting gap modulation

TL;DR

This paper introduces the 'pair-breaking scattering interference' mechanism as a universal explanation for coherence peak modulations in various superconductors, challenging the interpretation of pair density waves without normal state conductance changes.

Contribution

It proposes a new, general mechanism for coherence peak modulations in superconductors, providing a physical picture applicable across different materials.

Findings

Explains wavevectors and particle-hole symmetry of modulations

Accounts for Zeeman-field dependence of coherence peaks

Serves as a caution against misinterpreting pair density waves

Abstract

We propose the ``pair-breaking scattering interference" as a general source of coherence peak modulations in superconductors. Assuming this mechanism, we present a simple physical picture for the coherence peak modulations in overdoped cuprate Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+\delta}$ (Bi-2223), ferromagnetic iron pnictide EuRbFe$_4$As$_4$ (Eu-1144), and kagome metals $A$V$_3$Sb$_5$ ($A=$ K, Rb, and Cs). Specifically, we explain the wavevectors, the particle-hole symmetry, and the dependence on the internal or external Zeeman-field of the coherence peak modulations. This work is intended as a cautious reminder to the scientific community when asserting the existence of a pair density wave phenomenon in the absence of tunneling conductance modulations in the normal state.