# Observation of Caroli-de Gennes-Matricon Vortex States in YBa$_2$Cu$_3$O$_{7-\delta}$

## TL;DR

This study combines experimental tunneling measurements and theoretical modeling to identify vortex core states in YBa2Cu3O7−δ, suggesting that copper oxide superconductivity is conventional but masked by minority carriers.

## Contribution

It provides the first positive identification of vortex states in copper oxide superconductors through combined experimental and theoretical approaches.

## Key findings

- Vortex core states are present but weak in YBa2Cu3O7−δ.
- Variations in vortex spectra are explained by vortex interactions and disorder.
- Superconductivity in copper oxides may be conventional with minority carriers.

## Abstract

The copper oxides present the highest superconducting temperature and properties at odds with other compounds, suggestive of a fundamentally different superconductivity. In particular, the Abrikosov vortices fail to exhibit localized states expected and observed in all clean superconductors. We have explored the possibility that the elusive vortex-core signatures are actually present but weak. Combining local tunneling measurements with large-scale theoretical modeling, we positively identify the vortex states in YBa$_2$Cu$_3$O$_{7-\delta}$. We explain their spectrum and the observed variations thereof from one vortex to the next by considering the effects of nearby vortices and disorder in the vortex lattice. We argue that the superconductivity of copper oxides is conventional, but the spectroscopic signature does not look so because the superconducting carriers are a minority.