Imaging the essential role of spin-fluctuations in high-Tc superconductivity

TL;DR

This study uses scanning tunneling spectroscopy to explore how spin fluctuations influence high-temperature superconductivity in Bi-2223, revealing a local collective mode likely linked to spin resonance.

Contribution

It demonstrates that the dip feature in tunneling spectra accurately measures a collective mode associated with spin fluctuations in high-Tc cuprates.

Findings

The superconducting gap and dip are modulated by the lattice superstructure.

The dip energy correlates with the collective mode, likely the (pi,pi) spin resonance.

The collective mode energy varies with doping.

Abstract

We have used scanning tunneling spectroscopy to investigate short-length electronic correlations in three-layer Bi2Sr2Ca2Cu3O(10+d) (Bi-2223). We show that the superconducting gap and the energy Omega_dip, defined as the difference between the dip minimum and the gap, are both modulated in space following the lattice superstructure, and are locally anti-correlated. Based on fits of our data to a microscopic strong-coupling model we show that Omega_dip is an accurate measure of the collective mode energy in Bi-2223. We conclude that the collective mode responsible for the dip is a local excitation with a doping dependent energy, and is most likely the (pi,pi) spin resonance.