Photonic bilayer Chern insulator with corner states
arxiv(2024)
摘要
Photonic Chern insulators can be implemented in gyromagnetic photonic
crystals with broken time-reversal (TR) symmetry. They exhibit gapless chiral
edge states (CESs), enabling unidirectional propagation and demonstrating
exceptional resilience to localization even in the presence of defects or
disorders. However, when two Chern insulators with opposite Chern numbers are
stacked together, this one-way nature can be nullified, causing the originally
gapless CESs to become gapped. Recent theoretical works have proposed achieving
such a topological phase transition in condensed matter systems using
antiferromagnetic thin films such as MnBi2Te4 or by coupling two quantum
spin/anomalous Hall insulators, but these approaches have yet to be realized
experimentally. In a bilayer gyromagnetic photonic crystal arranged in an
antiferromagnetic layer configuration, our experimental observations reveal
that interlayer coupling initiates a transition from a Chern insulating phase
to a higher-order topological phase. This transition results in the gapping of
CESs and triggers the emergence of corner states within the bandgap. The corner
mode energy within the gap can be attributed to CESs interaction, forming a
Jackiw-Rebbi topological domain wall mode at the corner. These states exhibit
heightened resilience against defects, setting them apart from their
time-reversal symmetric counterparts.
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