# Non-reciprocal wave propagation in discretely modulated spatiotemporal plates

## TL;DR

This paper introduces a general plane wave expansion method for analyzing non-reciprocal wave propagation in discretely modulated spatiotemporal plates, demonstrating how such materials can break symmetry and violate reciprocity in wave transmission.

## Contribution

It presents a novel, general formulation of the Plane Wave Expansion Method applicable to 2D spatiotemporal unit cells and explores materials that break mirror symmetry in momentum space.

## Key findings

- Validated dispersion profiles with numerical simulations.
- Demonstrated non-reciprocal wave propagation in modulated plates.
- Showed the ability to violate reciprocity principle in wave transmission.

## Abstract

We investigate non-reciprocal wave propagation in spatiotemporal phononic plates. In particular, the first goal of this manuscript is to present a general formulation of the Plane Wave Expansion Method (PWEM) that, in contrast with previous works, is applicable to any class of 2D spatiotemporal unit cells whose properties can be expanded in traveling plane waves. The second goal is to exploit this analysis tool in order to study a new class of materials capable of violating mirror symmetry in momentum space, therefore breaking reciprocity principle along different wave propagation directions. This is obtained by considering the plate elastic properties to be discretely modulated in space and continuously in time. Theoretical dispersion profiles are validated and compared with numerical simulations.