Relaying Topological Interface States for Negative Refraction of Bulk Waves

TL;DR

This paper demonstrates a novel method to achieve negative refraction of bulk waves using topological interface states in valley photonic crystals, verified through microwave experiments, opening new avenues for wave manipulation.

Contribution

It introduces a topological approach to negative refraction via TISs in VPCs, a novel application of topological physics in bulk wave control.

Findings

Negative lateral shifts caused by TISs induce negative refraction.

Stacking VPC interfaces relays lateral shifts, enhancing wave control.

Experimental verification in microwave regime confirms the scheme's feasibility.

Abstract

Topological notions in physics have become a powerful perspective that leads to the discoveries of topological interface states (TISs). In this work, we present a scheme to achieve negative refraction by leveraging the properties of TISs in a valley photonic crystal (VPC). Due to the chiral characteristics, one type of the TISs deterministically possesses negative dispersion relation, which can cause an obliquely incident wave to undergo a negative lateral shift. By stacking multiple VPC interfaces, the TIS-induced lateral shifts can relay in the transmitted wave towards the far side of incidence. The resultant outgoing wave appears to have undergone negative refraction. This finding is verified in microwave experiments. Our scheme opens new application scenarios for topological systems in bulk wave manipulations.