Synopsis: Snowflake Topological Insulator

A two-dimensional array of holes shaped like snowflakes could route acoustic waves along an internal edge without any wave backscattering.
Synopsis figure
C. Brendel/Max Planck Institute for the Science of Light

Acoustic versions of topological insulators channel sound waves along their surfaces or edges but not in their bulk. They might improve acoustic technologies because the waves travel in the devices without the backscattering caused by impurities and structural disorder. But the devices have yet to reach nanoscale dimensions, which would enable the building of high-performance integrated acoustic circuits. Florian Marquardt from the Max Planck Institute for the Science of Light, Germany, and colleagues now propose that a two-dimensional array of holes fashioned like snowflakes could be turned into an acoustic topological insulator with nanoscale dimensions.

Two-dimensional arrays of snowflake-shaped holes have previously been built and have proven their worth. For example, they have been used to trap light and sound together. Marquardt and co-workers use so-called finite-element simulations, complemented by a derivation of the Hamiltonian for wave propagation in the array, to demonstrate that a simple change to the array can make it an acoustic topological insulator. The change involves creating two contiguous domains: one in which the radius of every third hole in the array is increased and the other in which that same radius is decreased. This yields a structure that does not transport sound waves in the interior of the domains but routes the waves along the edge between the domains without any backscattering. The team reckons the structure could be readily made in the lab using available nanofabrication techniques.

This research is published in Physical Review B.

­–Ana Lopes

Ana Lopes is a Senior Editor of Physics.


More Features »


More Announcements »

Subject Areas

Topological InsulatorsAcoustics

Previous Synopsis

Next Synopsis

Related Articles

Synopsis: Seeing Anyons with an STM
Quantum Physics

Synopsis: Seeing Anyons with an STM

A scanning tunneling microscope might detect unambiguous signatures of anyons in graphene. Read More »

Synopsis: Having the Edge on Optical Losses
Topological Insulators

Synopsis: Having the Edge on Optical Losses

An optical version of a topological insulator exhibits edge states that could be used to reduce scattering losses in optical waveguides. Read More »

Focus: Aquatic Eavesdropping

Focus: Aquatic Eavesdropping

A structured membrane enhances sound transmission across a water-air boundary, allowing underwater sounds to be heard in the air above. Read More »

More Articles