  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.
