Phonon-assisted Casimir interactions between piezoelectric materials

TL;DR

This paper investigates how phonon-electromagnetic interactions in piezoelectric materials can be used to modulate and distinguish Casimir forces, revealing new control mechanisms based on phonon properties.

Contribution

It introduces a real-frequency approach to calculate Casimir forces in piezoelectrics, accounting for complex phonon-electromagnetic couplings beyond standard methods.

Findings

Piezoelectric materials allow control of Casimir forces via phonon properties.

Different surface phonon polaritons can be distinguished through Casimir interactions.

The approach enables analysis at finite temperatures and complex phonon regimes.

Abstract

The strong coupling between electromagnetic field and lattice oscillation in piezoelectric materials gives rise to phonon polariton excitations. Such quasiparticles open up new directions in modulating the ubiquitous Casimir force. Here by utilizing the generalized Born-Huang hydrodynamics model, three types of phonons in piezoelectrics are studied: longitudinal optical phonon, transverse optical phonon and phonon polariton. The phonon-electromagnetic coupling results in a complex set of Fresnel reflection matrices which prevents the utilization of the standard Lifshitz approach for calculating Casimir forces in the imaginary frequency domain. Our calculations are based on an approach within real frequency and finite temperatures, through which various regimes of the Casimir interaction are examined. Our study shows that piezoelectrics emerge as a set of materials where this ubiquitous force can be controlled via phonon properties for the first time. The Casimir interaction appears as a suitable means to distinguish between different types of surface phonon polaritons associated with different structural piezoelectric polytypes.