Higher-order topological superconductivity in twisted bilayer graphene

Twisted bilayer graphene, by nature of its symmetries (like the approximate particle-hole symmetry) and anomalous band structure, realizes a higher-order topological superconductor when $s$-wave pairing is introduced via proximity. Here, the authors demonstrate this exotic phase numerically and analytically, and illustrate a multitude of consequences: zero modes bound to Abrikosov vortices, the fractional Josephson effect, and much more.