  In this work, ~100 nm wide quantum anomalous Hall insulator (QAHI)
nanoribbons are etched from a two-dimensional QAHI film. One part of the
nanoribbon is covered with superconducting Nb, while the other part is
connected to an Au lead via two-dimensional QAHI regions. Andreev reflection
spectroscopy measurements were performed, and multiple in-gap conductance peaks
were observed in three different devices. In the presence of an increasing
magnetic field perpendicular to the QAHI film, the multiple in-gap peak
structure evolves into a single zero-bias conductance peak (ZBCP). Theoretical
simulations suggest that the measurements are consistent with the scenario that
the increasing magnetic field drives the nanoribbons from a multi-channel
occupied regime to a single channel occupied regime, and that the ZBCP may be
induced by zero energy Majorana modes as previously predicted [24]. Although
further experiments are needed to clarify the nature of the ZBCP, we provide
initial evidence that quasi-1D QAHI nanoribbon/superconductor heterostructures
are new and promising platforms for realizing zero-energy Majorana modes.
