Anomalous Fraunhofer-like patterns in quantum anomalous Hall Josephson junctions

The intriguing interplay between topology and superconductivity has attracted significant attention, given its potential for realizing topological superconductivity. In the quantum anomalous Hall insulators (QAHIs)-based junction, the supercurrents are carried by the chiral edge states, characterized by a <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mn>2</a:mn><a:msub><a:mi mathvariant="normal">Φ</a:mi><a:mn>0</a:mn></a:msub></a:mrow></a:math> magnetic flux periodicity (<c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:msub><c:mi mathvariant="normal">Φ</c:mi><c:mn>0</c:mn></c:msub><c:mo>=</c:mo><c:mi>h</c:mi><c:mo>/</c:mo><c:mn>2</c:mn><c:mi>e</c:mi></c:mrow></c:math> is the flux quantum, <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mi>h</e:mi></e:math> the Planck constant, and <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"><f:mi>e</f:mi></f:math> the electron charge). However, experimental observations indicate the presence of bulk carriers in QAHI samples due to magnetic dopants. In this study, we reveal a systematic transition from edge-state to bulk-state dominant supercurrents as the chemical potential varies from the bulk gap to the conduction band. This results in an evolution from a <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:mrow><g:mn>2</g:mn><g:msub><g:mi mathvariant="normal">Φ</g:mi><g:mn>0</g:mn></g:msub></g:mrow></g:math>-periodic oscillation pattern to an asymmetric Fraunhofer pattern. Furthermore, a Fraunhoher-like pattern emerges due to the coexistence of chiral edge states and bulk states caused by magnetic domains, even when the chemical potential resides within the gap. These findings not only advance the theoretical understanding but also pave the way for the experimental discovery of the chiral Josephson effect based on QAHI doped with magnetic impurities. Published by the American Physical Society 2024