Abstract
Topological photonics has emerged as a promising field in photonics that is able to shape the science and technology of light. As a significant degree of freedom, valley is introduced to design and construct photonic topological phases, with encouraging recent progress in applications ranging from on‐chip communications to terahertz lasers. Herein, the development of topological valley photonics is reviewed, from both perspectives of fundamental physics and practical applications. The unique valley‐contrasting physics determines that the bulk topology and the bulk‐boundary correspondence in valley photonic topological phases exhibit different properties from other photonic topological phases. Valley conservation allows not only robust propagation of light through sharp corners, but also 100% out‐coupling of topological states to the surrounding environment. Finally, robust valley transport requires no magnetic materials or the complex construction of photonic pseudospin and, thus, can be integrated on compact photonic platforms for future technologies.
Highlights
Topological photonics has emerged as a promising field in photonics that is able was inspired by the concept of energy to shape the science and technology of light
We have reviewed the development of topological valley photonics from both perspectives of fundamental physics and practical applications
Different from other photonic topological phases, such as the quantum Hall and quantum spin Hall (QSH) phases, the nontrivial topology in a valley-Hall topological phase is not defined globally over the entire Brillouin zone, but is valid only in the vicinity of a valley. This sharp difference determines that the bulk-boundary correspondence is applicable to topological states not at the edges, in general, but at the domain walls between two valley photonic systems with opposite settings
Summary
The valley-Hall effect was first realized in MoS2 in 2014,[13] and the topological valley transport was first observed in bilayer graphene in 2015.[14]. Orbit coupling, a topologically nontrivial bandgap can be induced In this case, a topological insulator protected by T is created.[41,42,43,44] Similar to quantum Hall phase, this QSH phase is characterized by integer-valued global quantities, such as Z2 index or spin Chern number.[42,45] The third method to gap out the Dirac points is using the on-site energy detuning (i.e., M 61⁄4 0). It shall be pointed out that, these edge states at a natural zigzag termination do not exhibit valley-contrasting physics, one can still locally modify the edges to tune the edge states from gapped flat bands to gapless valley-locked bands.[50] There is another type of boundary in valley systems: an interface between two lattices with opposite on-site detuning (i.e., opposite signs of M).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
