Valley-dependent Corner States in Honeycomb Photonic Crystal without Inversion Symmetry

TL;DR

This paper investigates valley-dependent topological corner states in honeycomb photonic crystals lacking inversion symmetry, revealing corner-specific topological states linked to valley Chern numbers, with potential for experimental realization.

Contribution

It demonstrates the existence of valley-dependent corner states in non-inversion symmetric honeycomb photonic crystals, highlighting their dependence on corner orientation and providing a platform for higher-order topological photonics.

Findings

Corner states appear at 60° corners but not others.

Breaking inversion symmetry induces contrasting valley Chern numbers.

Platform suitable for experimental exploration of valley-dependent topology.

Abstract

We study topological states of honeycomb photonic crystals in absence of inversion symmetry using plane wave expansion and finite element methods. The breaking of inversion symmetry in honeycomb lattice leads to contrasting topological valley indices, i.e., the valley-dependent Chern numbers in momentum space. We find that the topological corner states appear for 60$^\circ$ degree corners, but absent for other corners, which can be understood as the sign flip of valley Chern number at the corner. Our results provide an experimentally feasible platform for exploring valley-dependent higher-order topology in photonic systems.