Sound Vortices

At Phonometa (Christensen’s Research Group), they’re specialists in physical acoustics and they’re finding acoustic analogues to an amount of physical processes.

In their last published work they show that, in Dr. Christensen own words “a Majorana‐like bound state can be engineered in artificial acoustic lattices thanks to a Jackiw–Rossi vortex, which is the analog of a topological superconductor vortex. Such vortex is created by introducing a Kekulé texture to the man‐made lattice of rigid cylinders. We also show how this binding mechanism can be well explained by a topological pumping process comprising adiabatic variations of the cylinder radii, which concentrates strong acoustic energy to the lattice center as shown in the cover image”.

This picture we made to illustrate the process, and under close collaboration with Dr. Johan Christensen and Dr Penglin Gao, was featured in the front cover of Advanced Quantum Technologies.

Listen to your heart!

Topological insulators (TIs) are way beyond my understanding but at the same time I cant help but appreciate its beauty. TIs are usually associated with photonics but are showing to be useful also in the fields of acoustics and mechanics. Dr. Johan Christensen in a collaborative research between Spain and China (Universidad Carlos III de Madrid and Nanjing University) has “experimentally explored topologically robust corner states across three different frequency bands,  measured sound intensity concentration in the long wavelength regime comprising highly confined corner states of diameter 50 times smaller than the sound wavelength”.

As a proof of concept, they’ve designed a physical pattern that produces an intensity sound pattern in a beautiful heart shape: art and science at its best! Their research has been published in Advanced Materials. The hallmark and key manifestation of topological states is the robustness against defects. In this context, the authors additionally demonstrate that the proposed deep‐subwavelength TI displays remarkable resilience against bulk disorder over the said frequency area, making this concept remarkably robust for real world applications.