Non-Hermitian and time-modulated topological sound

Baile Zhang

doi:10.1117/12.2594052

1 August 2021 Non-Hermitian and time-modulated topological sound

Baile Zhang

Proceedings Volume 11796, Active Photonic Platforms XIII; 117961J (2021) https://doi.org/10.1117/12.2594052
Event: SPIE Nanoscience + Engineering, 2021, San Diego, California, United States

Abstract

Topological photonics/acoustics utilizes classical waves to emulate topologically nontrivial phases originally developed in condensed matter systems such as topological insulators. While the band topology concepts are originally defined in Hermitian context, the classical-wave systems are intrinsically non-Hermitian, due to the inevitable loss and/or deliberately added gain. Here we will introduce some of our recent works in developing acoustic topological states that have no counterparts in condensed matter systems. The first is about non-Hermiticity-driven topological phase transition. This involves the demonstration of topological edge states in a 1D acoustic lattice and topological corner states in a 2D acoustic lattice. The second is about acoustic non-Hermitian skin effect from twisted winding topology. The twisted winding topology consists of two oppositely oriented loops with a contact point in between. We show that this topology dramatically modifies the non-Hermitian skin effect by causing bulk states collapse towards two directions. The contact point corresponds to an extended Bloch-wave-like bulk states. The third is a Floquet higher-order topological insulator realized in a 3D acoustic structure, whose third dimension serves as an effective time-dependent drive. All the above show novel topological physics on the platform of acoustic waves.

Conference Presentation

Citation Download Citation

Baile Zhang "Non-Hermitian and time-modulated topological sound", Proc. SPIE 11796, Active Photonic Platforms XIII, 117961J (1 August 2021); https://doi.org/10.1117/12.2594052

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