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Edge State Induced Andreev Oscillation in Quantum Anomalous Hall Insulator-Superconductor Junctions

We study the quantum Andreev oscillation induced by interference of the edge chiral Majorana fermions in junctions made of quantum anomalous Hall (QAH) insulators and superconductors (SCs). We show two chiral Majorana fermions on a QAH edge with SC proximity generically have a momentum difference $Δk$, which depends on the chemical potentials of both the QAH insulator and the SC. Due to the spatial interference induced by $Δk$, the longitudinal conductance of QAH-SC junctions oscillates with respect to the edge lengths and the chemical potentials, which can be probed via charge transport. Furthermore, we show the dynamical SC phase fluctuation will give rise to a geometrical correction to the longitudinal conductance of the junctions.