EQuAL Seminar: Youngjoon Choi

Electric Field Control of Superconductivity and Quantized Anomalous Hall Effects in Rhombohedral Tetralayer Graphene 

Inducing superconducting correlations in chiral edge states is predicted to generate topologicallyprotected modes with exotic quantum statistics. Past experimental efforts have focused on engineeringinterfaces between superconducting materials and quantum Hall systems. We present rhombohedraltetralayer graphene as an ideal platform for these hybrid interfaces leveraging the gate-tuned groundstates between intrinsic superconductors and quantum anomalous Hall states. We find multiplesuperconducting states, including one phase with critical temperature Tc = 55mK at superlattice fillingv≈ −3.5 for layer polarization corresponding to a weak moire potential. Quantized anomalous Halleffect occurs at v = −1 for weak moire potential, with a measured Chern number |C| = 4. Remarkably,gate voltage can also trigger nonvolatile switching of chirality in the quantum anomalous Hall state,enabling reconfiguration of topological edge mode networks in devices with local gate. We also findfractional and integer Chern insulators at zero magnetic field via thermodynamic compressibilitymeasurements at v = +2/3 and +1. These findings open new possibilities for hybrid interfaces betweensuperconductors and topological edge states in the low-disorder limit.