Abstract
Topology has recently become a focus in condensed matter physics, arising from the research of quantum Hall effect and quantum spin Hall effect. The quantum spin Hall insulator, also known as two-dimensional topological insulator, is an insulator that has topologically nontrivial band properties unlike conventional insulators. Also the application of topology to superconductors with a full superconducting gap gives rise to topological superconductors, which work as platforms to support Majorana fermions.
Here we first address the robust quantum edge transport of topological insulators in InAs/GaSb quantum wells. Recent experimental results show that the quantized conductance from helical edge states is very robust against in-plane magnetic fields up to 12 Tesla. We construct a six-band effective model for the description of the quantum spin Hall effect in InAs/GaSb quantum wells. It is shown that the hidden edge Dirac point may account for the experimental results of robust edge transport. Next we investigate the interference effect of chiral Majorana fermions in topological superconductors of quantum anomalous Hall insulator/superconductor hybrid device. We propose a Majorana-Josephson interferometer to demonstrate the coherent transport of chiral Majorana fermions. In the Majorana-Josephson interferometer, Josephson junction works as a Majorana valve that polarizes and filters the chiral Majorana modes to produce the interference pattern. As a powerful tool to characterize quantum coherence, the Majorana-Josephson interferometer even has the potential to manipulate Majorana qubits.
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