Dark topological valley Hall edge solitons

• Main Authors: Ren, Boquan, Wang, Hongguang, Kompanets, Victor O, Kartashov, Yaroslav V, Li, Yongdong, Zhang, Yiqi
• Format: Journal Article
• Language: English
• Published: 29-06-2022
• Subjects: Physics - Optics; Physics - Pattern Formation and Solitons
• DOI: 10.48550/arxiv.2206.14460

Nanophotonics 10, 3559-3566 (2021) Topological edge solitons propagating along the edge of a photonic
topological insulator are localized self-sustained hybrid states that are
immune to de-fects/disorders due to protection of the edge states stemming from
nontrivial topology of the system. Here, we predict that exceptionally robust
dark valley Hall edge solitons may form at the domain walls between two
honeycomb lattices with broken inversion sym-metry. The underlying structure
can be created with femtosecond laser inscription, it possesses large bandgap
where well-localized dark edge solitons form, and in contrast to systems with
broken time-reversal symmetry, it does not require external magnetic fields or
complex longitudinal waveguide modulations for reali-zation of the topological
phase. We present the enve-lope equation allowing to construct dark valley Hall
edge solitons analytically. Such solitons propagate without radiation into the
bulk of the lattice, and can circumvent sharp corners, that allows to observe
their persistent circulation along the closed triangular domain wall boundary.
They survive over huge distances even in the presence of disorder in the
underlying lattice. We also investigate interactions of closely located dark
topological valley Hall edge solitons and show that they are repulsive and lead
to the formation of two grey edge solitons, moving with different group
velocities depart-ing from group velocity of the linear edge state on which
initial dark solitons were constructed. Our results illus-trate that nonlinear
valley Hall systems can support rich variety of new self-sustained topological
states and may inspire their investigation in other nonlinear systems, such as
atomic vapours and polariton condensates.