A universal explanation of tunneling conductance in exotic superconductors

TL;DR

This paper presents a universal theory explaining tunneling conductance in exotic superconductors, reconciling discrepancies between STS and ARPES measurements by showing side peaks are coherence-mediated features, not direct DOS indicators.

Contribution

The authors generalize a theory from mesoscopic Kondo systems to 2D exotic superconductors, providing a unified explanation for tunneling conductance features across different materials.

Findings

Side peaks in tunneling conductance are coherence-mediated, not direct DOS features.

Theoretical predictions align with ARPES measurements of the superconducting gap.

The approach unifies understanding of tunneling spectra in cuprate and pnictide superconductors.

Abstract

A longstanding mystery in understanding cuprate superconductors is the inconsistency between the experimental data measured by scanning tunneling spectroscopy (STS) and angle-resolved photoemission spectroscopy (ARPES). In particular, the gap between prominent side peaks observed in STS is much bigger than the superconducting gap observed by ARPES measurements. Here, we reconcile the two experimental techniques by generalising a theory which was previously applied to zero-dimensional mesoscopic Kondo systems to strongly correlated two-dimensional (2D) exotic superconductors. We show that the side peaks observed in tunneling conductance measurements in all these materials have a universal origin: They are formed by coherence-mediated tunneling under bias and do not directly reflect the underlying density of states (DOS) of the sample. We obtain theoretical predictions of the tunneling conductance and the density of states of the sample simultaneously and show that for cuprate and pnictide superconductors, the extracted sample DOS is consistent with the superconducting gap measured by ARPES.