Superconductivity and quantized anomalous Hall effect in rhombohedral graphene

Inducing superconducting correlations in chiral edge states is predicted to generate topologically protected zero energy modes with exotic quantum statistics1–6. Experimental efforts so far have focused on engineering interfaces between superconducting materials—typically amorphous metals—and semiconducting quantum Hall7–11 or quantum anomalous Hall12,13 systems. However, the strong interfacial disorder inherent in this approach can prevent the formation of isolated topological modes14–17. An appealing alternative is to use low-density flat band materials in which the ground state can be tuned between intrinsic superconducting and quantum anomalous Hall states using only the electric field effect. However, quantized transport and superconductivity have not been simultaneously achieved. Here we show that rhombohedral tetralayer graphene aligned to a hexagonal boron nitride substrate hosts a quantized anomalous Hall state at superlattice filling ν = −1 as well as a superconducting state at ν ≈ −3.5 at zero magnetic field. Gate voltage can also be used to actuate non-volatile switching of the chirality in the quantum anomalous Hall state18, allowing, in principle, arbitrarily reconfigurable networks of topological edge modes in locally gated devices. Thermodynamic compressibility measurements further show a topologically ordered fractional Chern insulator at ν = 2/3 (ref. 19)—also stable at zero magnetic field—enabling proximity coupling between superconductivity and fractionally charged edge modes. Finally, we show that, as in rhombohedral bi- and trilayers20–22, integrating a transition metal dichalcogenide layer to the heterostructure nucleates a new superconducting pocket20–24, while leaving the topology of the ν = −1 quantum anomalous Hall state intact. Our results pave the way for a new generation of hybrid interfaces between superconductors and topological edge states in the low disorder limit.