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Momentum Transfer in Quantum Nanophotonic Systems

Youssef Jeyar, Brahim Guizal, Mauro Antezza

Published Mar 29, 2026• 0 citations
OpenAlex

Abstract

Casimir–Lifshitz forces arising from quantum electromagnetic fluctuations provide a fundamental mechanism for momentum transfer at the nanoscale. In this work, we investigatehow graphene-based nanostructures and periodic gratings enable active control of these forcesin three representative configurations. First, we analyze the Casimir–Lifshitz interaction between a gold plate and a graphene-covered dielectric grating. We show that the combinationof graphene and periodic structuring leads to a strong enhancement of the force, reachingup to 130%, with pronounced thermal effects at submicron separations.Second, we study tunable nonadditivity effects in the Casimir–Lifshitz force between twographene strip gratings. Using a rigorous scattering-matrix framework, we demonstrate thatthe interaction strongly depends on geometry and graphene chemical potential, leading todeviations from additive approximations of up to 30%, which can be tuned in situ.Finally, we investigate normal and lateral Casimir forces acting on a nanoparticle above agraphene grating. We reveal stable and unstable lateral equilibrium positions and identifytwo regimes governed by the ratio between separation distance and grating period. Our results highlight the breakdown of additive approximations and demonstrate new opportunitiesfor controlling nanoscale momentum transfer using graphene-based nanophotonic structures.

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Optics Express•Apr 11, 2025•1 citation
Casimir–Lifshitz forces arising from quantum electromagnetic fluctuations provide a fundamental mechanism for momentum transfer at the nanoscale. In this work, we investigatehow graphene-based nanostructures and periodic gratings enable active control of these forcesin three representative configurations. First, we analyze the Casimir–Lifshitz interaction between a gold plate and a graphene-covered dielectric grating. We show that the combinationof graphene and periodic structuring leads to a strong enhancement of the force, reachingup to 130%, with pronounced thermal effects at submicron separations.Second, we study tunable nonadditivity effects in the Casimir–Lifshitz force between twographene strip gratings. Using a rigorous scattering-matrix framework, we demonstrate thatthe interaction strongly depends on geometry and graphene chemical potential, leading todeviations from additive approximations of up to 30%, which can be tuned in situ.Finally, we investigate normal and lateral Casimir forces acting on a nanoparticle above agraphene grating. We reveal stable and unstable lateral equilibrium positions and identifytwo regimes governed by the ratio between separation distance and grating period. Our results highlight the breakdown of additive approximations and demonstrate new opportunitiesfor controlling nanoscale momentum transfer using graphene-based nanophotonic structures.
We investigate the Casimir force on thin suspended dielectric layers covered with graphene, both theoretically and experimentally. Thermal effects of the Casimir force on graphene occur at separations significantly smaller compared to ordinary metals and dielectrics. At such small separations, the Casimir force is sufficiently strong to be measured experimentally. However, the presence of substrates to support the graphene significantly reduces the enhancement. We show theoretically that replacing the solid substrate beneath graphene with a thin dielectric membrane partially restores this strong thermal dependence. One of the interacting objects is a solid gold plate. The other object is a suspended dielectric membrane made of either 15 nm of silicon oxide or 13 nm silicon nitride, covered with graphene. At a separation of $\sim$500 nm, theoretical predictions yield changes in the Casimir pressure of up to 54 % and 40 % for silicon oxide and silicon nitride, respectively, when the temperature is increased from 10 K to 294 K. Measurements were performed for graphene on a suspended silicon nitride membrane at room temperature, using a gold-coated sphere attached to a cantilever as the force sensor. The measured force gradient is consistent with the theoretical prediction, although the thermal dependence could not be resolved, in part because of uncertainties in the optical properties of silicon nitride. Replacing a bulk substrate with a thin dielectric membrane covered with graphene provides a substantial reduction of the Casimir force, which may facilitate the stable operation of neutral nanomechanical elements at small separations.
Quantum and thermal electromagnetic fluctuations give rise to macroscopic phenomena such as Casimir–Lifshitz forces and radiative heat transfer. In this colloquium, I will introduce the common theoretical framework underlying these effects and discuss how they can be shaped and controlled through geometry, material properties, and nonequilibrium conditions. I will first discuss the giant Casimir torque arising between rotated metallic gratings, where a geometric transition at zero relative angle produces an anomalous torque enhancement and points toward the realization of a contactless quantum-vacuum torsional spring. I will then present a Kapitza-like mechanism for near-field radiative heat transfer, showing how rapid modulation of the vacuum gap or of the material response can alter the time-averaged thermal dynamics, shift stationary temperatures, and can stabilize or destabilize thermal steady states. Together, these examples illustrate emerging strategies for controlling mechanical forces and heat transport through shaping light–matter interactions.
Casimir forces, arising from quantum and thermal fluctuations, depend strongly on the electromagnetic susceptibilities of the interacting materials. Here, we theoretically investigate the Casimir force between two graphene sheets separated by a nanometer-thin layer of liquid water. We find that deviations from the bulk case can be as large as 24 \%, mostly due to the static susceptibility components. This effect does not decrease monotonically as a function of the layer thickness: it increases up to a maximum at 70 nm and it slowly declines to the bulk limit only at 1 micron. This is due to two competing effects: on one hand, the anisotropy decreases with the layer thickness; on the other hand, the relative contribution of the most anisotropic, static susceptibility components increases.
We investigate the fluctuation-induced Casimir interactions between two parallel graphene sheets carrying steady-state drift currents. The graphene properties are modeled based on the shifted Fermi disk model to capture the non-equilibrium optical response of the system. We find that the drift current introduces a repulsive correction to the perpendicular to the layers Casimir interaction, thereby reducing the overall attractive force. Although the correction is repulsive, it does not overcome the underlying attraction between the layers. It also generates a lateral force that opposes the carrier flow direction. Both contributions are studied in terms of distance and drift velocity functionalities showing pathways for Casimir force control.
Broadband optical response governs light-matter interactions across photonics, plasmonics, thermal radiation, and quantum fluctuation electrodynamics, yet determining a continuous dielectric function over many decades in frequency typically requires combining multiple spectroscopies, extrapolations, and material models. Here we show that quantum-fluctuation forces provide a route to broadband optical characterization. Casimir interactions depend on the dielectric response of materials across the electromagnetic spectrum, but this information is encoded through Lifshitz theory in a spectrally weighted and nontrivial way. By training physics-constrained supervised learning models on synthetic dielectric spectra and their corresponding Casimir force curves, we invert this relationship and constrain the complex permittivity of materials over more than seven orders of magnitude in frequency and provide an estimate of their values from force-distance data. The reconstruction reveals a direct separation-frequency correspondence: large separations constrain the free-carrier response, whereas shorter separations encode higher-frequency resonant structure. Applying the method to measured force gradients identifies the current experimental limits imposed by measurement noise, restricted separation range, and model complexity. These results establish fluctuation-induced forces as a spectrally weighted route to broadband optical characterization and define the experimental and physical limits that govern what spectral information is accessible from near-field quantum electromagnetic measurements.
This study proposes a nanophotonic structure that supports the generation and enhancement of the lateral Casimir-Polder (CP) force acting on atoms. By applying the two-dimensional anisotropic material, we demonstrate that both the spontaneous decay rate and the emission pattern of the atom exhibit distinct features by manipulating the parameters of the system. In particular, the exact numerical solutions of population dynamics reveal the occurrence of Rabi oscillations in the strong atom-field coupling case, where the Markovian results fail to describe this phenomenon. We also show that the asymmetric spatial distribution of the in-plane dipole radiation into surface plasmon modes is achievable for the system under consideration. Based on these intriguing properties, we predict the generation of the lateral CP force, where the transient evolution of the force indicates the periodical variation in both the direction and the amplitude under strong light-atom interaction conditions. Our findings have potential applications for novel optical nanotechnologies and devices, which provide a method for atom manipulation and trapping.