Bosonic excitations and electron pairing in an electron-doped cuprate superconductor

TL;DR

This study uses ultrafast optical spectroscopy to identify a dominant electronic bosonic mode, likely antiferromagnetic spin fluctuations, that strongly couples with charge carriers and drives superconductivity in electron-doped cuprates.

Contribution

It provides direct evidence linking a specific electronic bosonic mode to superconducting pairing in electron-doped cuprates, advancing understanding of the pairing mechanism.

Findings

Identified a bosonic mode of electronic origin with strong coupling near Tc.

Linked the mode to two-dimensional antiferromagnetic spin fluctuations.

Demonstrated the mode's role in accounting for superconducting pairing.

Abstract

Superconductivity originates from the coupling between charge carriers and bosonic excitations of either phononic or electronic origin. Identifying the most relevant pairing glue is a key step towards a clear understanding of the unconventional superconductivity. Here, by applying the ultrafast optical spectroscopy on the electron-doped cuprates La$_{1.9}$Ce$_{0.1}$CuO$_{4\pm\delta}$, we discern a bosonic mode of electronic origin that has the strongest coupling with the charge carriers near $T_c$. We argue that this mode is associated with the two-dimensional antiferromagnetic spin fluctuations, and can fully account for the superconducting pairing. Our work may help to establish a quantitative relation between bosonic excitations and superconducting pairing in electron-doped cuprates, and pave the way for systematic exploration of superconductivity and other collective phenomena in all correlated materials.