Dynamical Casimir Effects: The Need for Nonlocality in Time-Varying Dispersive Nanophotonics

TL;DR

This paper explores how nonlocality in time-varying dispersive nanophotonics is essential for accurately modeling dynamical Casimir effects, revealing that local models can produce nonphysical results and that nonlocality provides a more realistic description.

Contribution

It demonstrates the necessity of incorporating material nonlocality in models of dynamical Casimir effects to avoid nonphysical predictions and to capture effects overlooked by local theories.

Findings

Local models predict diverging emission rates, which are nonphysical.

Nonlocality regularizes emission rate predictions, making them finite.

Nonlocal effects cause a broadening of the emission rate distribution.

Abstract

Both real and virtual photons can be involved in light-matter interactions. A famous example of the observable implications of virtual photons -- vacuum fluctuations of the quantum electromagnetic field -- is the Casimir effect. Since quantum vacuum effects are weak, various mechanisms have been proposed to enhance and engineer them, ranging from static, e.g., strong optical resonances, to dynamic, e.g., systems with moving boundaries or time-varying optical properties, or a combination of them. In this Letter, we discuss the role of material nonlocality (spatial dispersion) in dynamical Casimir effects in time-varying frequency-dispersive nanophotonic systems. We first show that local models may lead to nonphysical predictions, such as diverging emission rates of entangled polariton pairs. We then theoretically demonstrate that nonlocality regularizes this behavior by correcting the asymptotic response of the system for large wavevectors and reveals physical effects missed by local models, including a significant broadening of the emission rate distribution, which are relevant for future experimental observations. Our work sheds light on the importance of nonlocal effects in this new frontier of nanophotonics.