# Defect-induced magnetism and Yu-Shiba-Rusinov states in twisted bilayer graphene

## TL;DR

This study demonstrates how atomic defects, such as hydrogen adatoms and vacancies, induce local magnetic moments and Yu-Shiba-Rusinov states in twisted bilayer graphene, affecting its superconducting properties.

## Contribution

It provides first-principles and tight-binding evidence that defects create magnetic moments and in-gap states in twisted bilayer graphene, revealing new defect-superconductivity interactions.

## Key findings

- Hydrogen adatoms induce triple-point crossings.
- Vacancies cause self-doping and symmetry breaking.
- Defects lead to local magnetism and Yu-Shiba-Rusinov states.

## Abstract

Atomic defects have a significant impact in the low-energy properties of graphene systems. By means of first-principles calculations and tight-binding models we provide evidence that chemical impurities modify both the normal and the superconducting states of twisted bilayer graphene. A single hydrogen atom attached to the bilayer surface yields a triple-point crossing, whereas self-doping and three-fold symmetry-breaking are created by a vacant site. Both types of defects lead to time-reversal symmetry-breaking and the creation of local magnetic moments. Hydrogen-induced magnetism is found to exist also at the doping levels where superconductivity appears in magic angle graphene superlattices. As a result, the coexistence of superconducting order and defect-induced magnetism yields in-gap Yu-Shiba-Rusinov excitations in magic angle twisted bilayer graphene.