We present a numerical approach for the solution of EM scattering from a dielectric cylinder partially covered with graphene. It is based on a clas- sical Fourier-Bessel expansion of the fields inside and outside the cylinder to which we apply the ad-hoc boundary conditions in the presence of graphene. Due to the singular nature of the electric field at the ends of the graphene sheet, we introduce auxiliary boundary conditions to better take this reality into ac- count. The result is a very simple and very efficient method allowing the study of diffraction from such structures. Our ultimate goal is to apply this approach to radiative heat transfer between graphene coated cylinders and planes.

We present a theoretical study of near-field radiative thermal rectification combining phase-transition and high-infrared-transmittance materials. The phase-transition material vanadium dioxide (VO2), with a metal–insulator transition near 341 K, is utilized under a reasonable temperature. Four types of high-infrared-transmittance materials, including potassium bromide, sodium chloride, polyethylene, andmagnesium fluoride, are introduced as thin film substrates under a VO2 grating on one side of the near-field rectifier. We explore the effects of various high-infrared-transmittance thin-film substrates and relevant geometric parameters on the thermal rectification of the device. The results show that thermal rectification can be greatly enhanced by using a one-dimensional VO2 grating backed with a high-infraredtransmittance thin-film substrate. With the introduction of a high-infrared-transmittance substrate, the rectification ratio is dramatically boosted due to the enhancement of the substrate transmittance. This work predicts a remarkable rectification ratio as high as 161—greater than the recently reported peak values for comparable near-field radiative thermal rectification. The results outlined herein will shed light on the rapidly expanding fields of nanoscale thermal harvesting, conversion, and management.

This work demonstrates the magnetic field-induced spectral properties of metamaterials incorporating both indium antimonide (InSb) and tungsten (W) in the terahertz (THz) frequency regime. Nanostructure materials, layer thicknesses and surface grating fill factors are modified, impacting light-matter interactions and consequently modifying thermal emission. We describe and validate a method for determining spectral properties of InSb under an applied direct current (DC) magnetic field, and employ this method to analyze how these properties can be tuned by modulating the field magnitude. Notably, an InSb-W metamaterial exhibiting unity narrowband emission is designed, suitable as an emitter for wavelengths around 55 µm (approximately 5.5 THz), which is magnetically tunable in bandwidth and peak wavelength.

We will discuss recent results: (i) on the Casimir torque between two metallic one-dimensionalgratings rotated by an angle θ with respect to each other; and (ii) on the Casimir force occurring between interpenetrating gratings. These findings pave the way to the design of acontactless quantum vacuum torsional spring, and sensors with possible relevance to microand nanomechanical devices.

Twisted two-dimensional bilayer anisotropy materials exhibit many exotic physical phenomena. Manipulating the “twist angle” between the two layers enables the hybridization phenomenon of polaritons, resulting in fine control of the dispersion engineering of the polaritons in these structures. Here, combined with the hybridization phenomenon of anisotropy polaritons, we study theoretically the near-field radiative heat transfer (NFRHT) between two twisted hyperbolic systems. These two twisted hyperbolic systems are mirror images of each other. Each twisted hyperbolic system is composed of two graphene gratings, where there is an angle φ between these two graphene gratings. By analyzing the photonic transmission coefficient as well as the plasmon dispersion relation of the twisted hyperbolic system, we prove the enhancement effect of the topological transitions of the surface state at a special angle [from open (hyperbolic) to closed (elliptical) contours] on radiative heat transfer. Meanwhile the role of the thickness of dielectric spacer and vacuum gap on the manipulating the topological transitions of the surface state and the NFRHT are also discussed. We predict the hysteresis effect of topological transitions at a larger vacuum gap, and demonstrate that as the thickness of the dielectric spacer increases, the transition from the enhancement effect of heat transfer caused by the twisted hyperbolic system to a suppression.

We perform a detailed analysis of electronic polarizability of graphene with different theoretical approaches.From Kubo’s linear response formalism, we give a general expression of frequency and wave-vector dependentpolarizability within the random phase approximation. Four theoretical approaches have been applied to thesingle-layer graphene and their differences are on the band overlap of wave functions. By comparing with theab initio calculation, we discuss the validity of methods used in literature. Our results show that the tightbinding method is as good as the time-demanding ab initio approach in calculating the polarizability of graphene.Moreover, due to the special Dirac-cone band structure of graphene, the Dirac model reproduces results of thetight-binding method for energy smaller than 3 eV. For doped graphene, the intraband transitions dominateat low energies and can be described by the Lindhard formula for two-dimensional electron gases. At zerotemperature and long-wavelength limit, with the relaxation time approximation, all theoretical methods reduceto a long-wave analytical formula and the intraband contributions agree to the Drude polarizability of graphene.Effects of electrical doping and temperature are also discussed. This work may provide a solid reference forresearches and applications of the screening effect of graphene.

Quantum fluctuations give rise to Casimir forces between two parallel conducting plates, the magnitude of which increases monotonically as the separation decreases. By introducing nanoscale gratings to the surfaces, recent advances have opened opportunities for controlling the Casimir force in complex geometries. Here, we measure the Casimir force between two rectangular silicon gratings. Using an on-chip detection platform, we achieve accurate alignment between the two gratings so that they interpenetrate as the separation is reduced. Just before interpenetration occurs, the measured Casimir force is found to have a geometry dependence that is much stronger than previous experiments, with deviations from the proximity force approximation reaching a factor of ~500. After the gratings interpenetrate each other, the Casimir force becomes non-zero and independent of displacement. This work shows that the presence of gratings can strongly modify the Casimir force to control the interaction between nanomechanical components.