3 research outputs found
Proximity-induced quasi-one-dimensional superconducting quantum anomalous Hall state: a promising scalable top-down approach towards localized Majorana modes
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
Exchange-biased quantum anomalous Hall effect
The quantum anomalous Hall (QAH) effect is characterized by a dissipationless
chiral edge state with a quantized Hall resistance at zero magnetic field.
Manipulating the QAH state is of great importance in both the understanding of
topological quantum physics and the implementation of dissipationless
electronics. Here, we realized the QAH effect in the magnetic topological
insulator Cr-doped (Bi,Sb)2Te3 (CBST) grown on an uncompensated
antiferromagnetic insulator Al-doped Cr2O3. Through polarized neutron
reflectometry (PNR), we find a strong exchange coupling between CBST and
Al-Cr2O3 surface spins fixing interfacial magnetic moments perpendicular to the
film plane. The interfacial coupling results in an exchange-biased QAH effect.
We further demonstrate that the magnitude and sign of the exchange bias can be
effectively controlled using a field training process to set the magnetization
of the Al-Cr2O3 layer. Our work demonstrates the use of the exchange bias
effect to effectively manipulate the QAH state, opening new possibilities in
QAH-based spintronics