Examinando por Autor "Antezza, Mauro"

Mostrando 1 - 4 de 4

Confinement-Induced Nonlocality and Casimir Force in Transdimensional Systems
(The Royal Society of Chemistry, 2023-10-09) Bondarev, Igor V.; Pugh, Michael D.; Rodriguez-Lopez, Pablo; Woods, Lilia M.; Antezza, Mauro
We study within the framework of the Lifshitz theory the long-range Casimir force for in-plane isotropic and anisotropic free-standing transdimensional material slabs. In the former case{,} we show that the confinement-induced nonlocality not only weakens the attraction of ultrathin slabs but also changes the distance dependence of the material-dependent correction to the Casimir force to go as contrary to the ∼1/l dependence of that of the local Lifshitz force. In the latter case{,} we use closely packed array of parallel aligned single-wall carbon nanotubes in a dielectric layer of finite thickness to demonstrate strong orientational anisotropy and crossover behavior for the inter-slab attractive force in addition to its reduction with decreasing slab thickness. We give physical insight as to why such a pair of ultrathin slabs prefers to stick together in the perpendicularly oriented manner{,} rather than in the parallel relative orientation as one would customarily expect.
Electric conductivity in graphene: Kubo model versus a nonlocal quantum field theory model
(American Physical Society, 2025-03-26) Rodriguez-Lopez, Pablo; Wang, Jian-Sheng; Antezza, Mauro
We compare three models of graphene electric conductivity: a non-local Kubo model, a local model derived by Falkovsky, and finally, a non-local quantum field theory (QFT) polarization-based model. These models are supposed to provide consistent results since they are derived from the same Hamiltonian. While we confirm that the local model is a proper $\textbf{q}\to\textbf{0}$ limit of both the non-local Kubo and the non-local QFT model (once losses are added to this last model), we find hard inconsistencies in the non-local QFT model as derived and currently used in literature. In particular, in the genuine non-local region ($\textbf{q}\neq\textbf{0}$), the available QFT model shows an intrinsic non-physical plasma-like behavior for the interband transversal electric conductivity at low frequencies (even after introducing the unavoidable losses). The Kubo model, instead, shows the expected behavior, i.e., an almost constant electric conductivity as a function of frequency $\omega$ with a gap for frequencies $\hbar\omega < \sqrt{(\hbar v_{F}q)^{2} + 4m^{2}}$. We show that the Kubo and QFT models can be expressed using an identical Polarization operator $\Pi_{\mu\nu}(\omega,\textbf{q})$, but they employ different expressions for the electric conductivity $\sigma_{\mu\nu}(\omega,\textbf{q})$. In particular, the Kubo model uses a standard regularized expression, a direct consequence of Ohm's Law and causality, as we rigorously re-derive. We show that, once the standard regularized expression for $\sigma_{\mu\nu}(\omega,\textbf{q})$ is used in the QFT model, and losses are included, the Kubo and QFT model coincide, and all its anomalies naturally disappear. Our findings show the necessity to appropriately define and regularize the electric conductivity to connect it with the available QFT model. This can be relevant for theory, predictions, and experimental tests in the nanophotonics and Casimir effect communities.
Giant anisotropy and Casimir phenomena: The case of carbon nanotube metasurfaces
(American Physical Society, 2024-01-17) Rodriguez-Lopez, Pablo; Le, Dai-Nam; Bondarev, Igor V.; Antezza, Mauro; Woods, Lilia M.
The Casimir interaction and torque are related phenomena originating from the exchange of electromagnetic excitations between objects. While the Casimir force exists between any types of objects, the materials or geometrical anisotropy drives the emergence of the Casimir torque. Here both phenomena are studied theoretically between dielectric films with immersed parallel single wall carbon nanotubes in the dilute limit with their chirality and collective electronic and optical response properties taken into account. It is found that the Casimir interaction is dominated by thermal fluctuations at sub-micron separations, while the torque is primarily determined by quantum mechanical effects. This peculiar quantum vs. thermal separation is attributed to the strong influence of reduced dimensionality and inherent anisotropy of the materials. Our study suggests that nanostructured anisotropic materials can serve as novel platforms to uncover new functionalities in ubiquitous Casimir phenomena.
Nonreciprocal heat flux via synthetic fields in linear quantum systems
(American Physical Society, 2023-10-03) Biehs, Svend-Age; Rodriguez-Lopez, Pablo; Antezza, Mauro; Agarwal, Girish S.
We study the heat transfer between N coupled quantum resonators with applied synthetic electric and magnetic fields realized by changing the resonator parameters by external drivings. To this end we develop two general methods, based on the quantum optical master equation and on the Langevin equation for N coupled oscillators where all quantum oscillators can have their own heat baths. The synthetic electric and magnetic fields are generated by a dynamical modulation of the oscillator resonance with a given phase. Using Floquet theory, we solve the dynamical equations with both methods, which allow us to determine the heat flux spectra and the transferred power. We apply these methods to study the specific case of a linear tight-binding chain of four quantum coupled resonators. We find that, in that case, in addition to a nonreciprocal heat flux spectrum already predicted in previous investigations, the synthetic fields induce here nonreciprocity in the total heat flux, hence realizing a net heat flux rectification.