Copropagation of antichiral edge states in the metallic phase requires the
bulk states as counterpropagating modes. Without the band gap protection, the
copropagation along the boundaries is easily scattered into the bulk and the
counterpropagation in the bulk is not robust against disorder and defects.
Here, we propose a novel time-reversal symmetric topological insulator holding
the synchronized in-gap edge states. To prevent the participation of bulk
states, we introduce the time-reversal symmetry to detach the edge states from
the bulk band, then the robust copropagation is realized through widening the
band gap across a metal-insulator transition with anisotropic
next-nearest-neighbor couplings. The time-reversal symmetry ensures the in-gap
edge states with opposite momenta as the counterpropagating modes. The
inversion symmetry protects the quantized polarization as a topological
invariant. The synchronized in-gap edge states not only enrich the family of
topological edge states, but also provide additional flexibility in the design
of reconfigurable topological optical devices. Our findings open a new avenue
for the tailored robust wave transport using the in-gap edge states for future
acousto-optic topological metamaterials.

Este artículo explora los viajes en el tiempo y sus implicaciones.

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