Soft self-assembly of Weyl materials for light and sound

TL;DR

This paper introduces a bottom-up self-assembly method to create three-dimensional photonic and phononic crystals with Weyl points, enabling topologically protected light and sound channels in soft materials.

Contribution

It develops a symmetry-driven pipeline for designing self-assembled Weyl materials, combining group theory and simulations, exemplified with block copolymer systems.

Findings

Identified symmetry constraints for Weyl points in self-assembled structures

Demonstrated topologically protected surface states in designed materials

Provided a practical design approach using block copolymer self-assembly

Abstract

Soft materials can self-assemble into highly structured phases which replicate at the mesoscopic scale the symmetry of atomic crystals. As such, they offer an unparalleled platform to design mesostructured materials for light and sound. Here, we present a bottom-up approach based on self-assembly to engineer three-dimensional photonic and phononic crystals with topologically protected Weyl points. In addition to angular and frequency selectivity of their bulk optical response, Weyl materials are endowed with topological surface states, which allows for the existence of one-way channels even in the presence of time-reversal invariance. Using a combination of group-theoretical methods and numerical simulations, we identify the general symmetry constraints that a self-assembled structure has to satisfy in order to host Weyl points, and describe how to achieve such constraints using a symmetry-driven pipeline for self-assembled material design and discovery. We illustrate our general approach using block copolymer self-assembly as a model system.