Tailoring higher-order topological phases via orbital hybridization

Abstract

Higher-order topological insulators (HOTIs) have attracted much attention in photonics due to the tightly localized disorder-robust corner and hinge states. Here, we reveal an unconventional HOTI phase with vanishing dipole and quadrupole polarizations. This phase arises in the array of evanescently coupled waveguides hosting degenerate $s$- and $d$-type orbital modes arranged in a square lattice with four waveguides in the unit cell. As we prove, the degeneracy of the modes with the different symmetry gives rise to the nontrivial topological properties rendering the system equivalent to the two copies of anisotropic two-dimensional Su-Schrieffer-Heeger model rotated by 90${}^{\circ }$ with respect to each other and based on $s\pm d$ hybridized orbitals. Our results introduce a route to tailor higher-order band topology leveraging both crystalline symmetries and accidental degeneracies of the different orbital modes.

13 pages, 9 figures

References in corpus (13)

• Scheme to Achieve Silicon Topological Photonics
• Electric Multipole Moments, Topological Multipole Moment Pumping, and Chiral Hinge States in Crystalline Insulators
• Time Reversal Polarization and a Z_2 Adiabatic Spin Pump
• Direct observation of corner states in second-order topological photonic crystal slabs
• Flat bands and Wigner crystallization in the honeycomb optical lattice
• Photonic topological pumping through the edges of a dynamical four-dimensional quantum Hall system
• Novel Topological Phase with Zero Berry Curvature
• Exploring 4D Quantum Hall Physics with a 2D Topological Charge Pump
• Topological orbital ladders
• p-band engineering in artificial electronic lattices
• Higher-order topological states mediated by long-range coupling in $D_4$-symmetric lattices
• Second-order topological corner states with ultracold atoms carrying orbital angular momentum in optical lattices
• Experimental observation of inter-orbital coupling

Cited by in corpus (2)

• Connecting Higher-Order Topology with the Orbital Hall Effect in Monolayers of Transition Metal Dichalcogenides
• A mono-atomic orbital-based 1D topological crystalline insulator