Topological Phononic Logic

TL;DR

This paper demonstrates a topological phononic logic gate for ultrasound that uses accidental degeneracies in a honeycomb lattice to switch between topological and trivial phases, enabling controllable waveguiding.

Contribution

It introduces a novel topological logic gate design exploiting accidental degeneracies, with a tunable phononic switch controlled by ultrasonic heating.

Findings

Degeneracy can be broken by six physical parameters.

A phononic switch transitions between topological waveguide and trivial insulator.

Design scheme applicable to photonic crystals and electronic transistors.

Abstract

Topological metamaterials have robust properties engineered from their macroscopic arrangement, rather than their microscopic constituency. They can be designed by starting from Dirac metamaterials with either symmetry-enforced or accidental degeneracy. The latter case provides greater flexibility in the design of topological switches, waveguides, and cloaking devices, because a large number of tuning parameters can be used to break the degeneracy and induce a topological phase. However, the design of a topological logic element--a switch that can be controlled by the output of a separate switch--remains elusive. Here we numerically demonstrate a topological logic gate for ultrasound by exploiting the large phase space of accidental degeneracies in a honeycomb lattice. We find that a degeneracy can be broken by six physical parameters, and we show how to tune these parameters to create a phononic switch that transitions between a topological waveguide and a trivial insulator by ultrasonic heating. Our design scheme is directly applicable to photonic crystals and may guide the design of future electronic topological transistors.