Coexistence of pseudospin- and valley-Hall-like edge states in a photonic crystal with C3v symmetry

Abstract

We demonstrate the coexistence of pseudospin-and valley-Hall-like edge states in a photonic crystal with C 3v symmetry, which is composed of three interlacing triangular sublattices with the same lattice constants. By tuning the geometry of the sublattices, three complete photonic band gaps with nontrivial topology can be created, one of which is due to the band inversion associated with the pseudospin degree of freedom at the point and the other two due to the gapping out of Dirac cones associated with the valley degree of freedom at the K, K points. The system can support triband pseudospin-and valley-momentum locking edge states at properly designed domain-wall interfaces. Furthermore, to demonstrate the novel interplay of the two kinds of edge states in a single configuration, we design a four-channel system, where the unidirectional routing of electromagnetic waves against sharp bends between two routes can be selectively controlled by the pseudospin and valley degrees of freedom. Our work combines the pseudospin and valley degrees of freedom in a single configuration and may provide more flexibility in manipulating electromagnetic waves with promising potential for multiband and multifunctional applications.

Experimental observation of topological large-area pseudo-spin-momentum-locking waveguide states with exceptional robustness

“…The LPWSs have great potential for practical applications, such as topological channel intersections, topological energy concentrators, topological cavities with tunable mode confinement, and high-capacity energy splitters. Compared to conventional topological edge states, LPWSs are more compatible with interfacing with existing waveguide-based photonic devices, making them appealing for applications in different scenarios, such as multiband, 53 reconfigurable, 29 wavelength division multiplexing, 54 , 55 and coexistence of different topological states 56 , 57 . For future works, it would be interesting to experimentally investigate the LPWSs at higher frequencies, such as terahertz, infrared, and optical frequencies, for more compact on-chip applications.…”

Passive topological waveguide controlled by the boundary of the patterned area of external magnetic field with the hybrid quantum Hall and valley Hall effects

“…By combining two structures with opposite topological phases, i.e. the valley Chern number, the valley topological edge states (VTESs) can be achieved [20][21][22][23]. To change the TES configuration, one has to change the bulky structure.…”

Topological phase transitions and Weyl semimetal phases in chiral photonic metamaterials

“…A richer phase diagram of the nonlocal chiral media is shown in figure 5(d). The locations (black curves) of Weyl points are obtained by equation (8). The curves of Weyl points also divide the whole zone into three sections.…”

“…It describes the invariance under continuous deformation [1][2][3][4][5]. The idea of topological phases in photonics stems from the exciting development of solid materials, which have fundamentally changed our understanding of the phase of matter [6][7][8][9][10][11][12][13][14][15][16]. The novel topological phases have been proposed and studied in photonic systems, including topological insulators [17], topological semimetals [18], and non-abelian topological charges [19].…”