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The black phosphorus (BP)/hexagonal boron nitride (hBN) Van der Waals heterostructure has great potential application in BP-based devices due to its higher stability than monolayer BP film. The near-field thermal radiation (NFTR) between two identical BP/hBN heterostructures with high electron density is studied to promote the application of BP-based devices. The BP/hBN heterostructures show a higher heat transfer coefficient (HTC) at a 10 nm gap distance compared to BP films with electron density n larger than 1 × 1013 cm−2, due to the coupling of surface plasmon polaritons (SPPs) and hyperbolic phonon polaritons (HPPs). Especially at n ≥ 3 × 1013 cm−2, the improvement is more than 100%. The SPPs and the HPPs couple into surface plasmon-phonon polaritons (SPPPs) out of the hyperbolic region and hyperbolic plasmon-phonon polaritons (HPPPs) inside. The SPPPs can achieve photon tunneling in the broader wavevector region than SPPs, making most of the contribution to heat transfer. The influences of the thickness of the hBN sheet and gap distance are also discussed. This scheme only effectively enhances NFTR for BP with high electron density at small nanogaps. After structural optimization, h = 2 nm is the optimal thickness for BP/hBN configuration with low electron density, such as n = 1 × 1013 cm−2. In contrast, large thickness h = 500 nm is optimal for BP with high electron density. At high electron density, a thick hBN sheet is prominent in enhancing the SPPPs in the frequencies below the type-I region and the HPPPs inside the type-II region. We further propose BP/hBN/BP heterostructures and find that HTC is further enhanced by 4.4% ~ 30.8% due to the more robust surface modes. Our work may contribute to developing BP-based near-field thermal devices and promote understanding the NFTR mechanism of BP/hBN heterostructure. [ABSTRACT FROM AUTHOR]

Modes have steadily influenced the understanding of physical systems through time. At least since the prediction of the Casimir effect, they also play a very important role in Casimir physics and in the understanding of the different phenomena typical of this research field. At equilibrium modes provide a direct connection between the zero-point energy and the existence of irreducible fluctuations in a quantum system, offering an anatomic view into the physics of the interaction. In nonequilibrium systems, modes can be decisive to understand the behavior of quantum fluctuation-induced phenomena, highlighting key aspects which determine their strength and their functional dependence. In this article we review some recent studies and results that highlight how modes impact Casimir physics and the central role they play in shaping our understanding of this area of research. [ABSTRACT FROM AUTHOR]

A novel interferometric technique for studies of exothermal chemical reactions at the water surface is presented. The key feature of the technique is the use of an air bubble as the interface which hosts coating molecules and at the same time acts as a subnanometer-sensitive Fabry-Perot interferometer which follows the bubble radius change after a chemical reaction with coating molecules. As an example we report measurements of a protonation reaction with dodecyl-amine (DA). A monolayer of the DA surfactant is formed at the gas-liquid interface of a millimeter-sized bubble immersed in a 10.6 pH solution. After the monolayer formation, the residual DA is removed from the bulk by gentle rinsing. Interference with the DA bulk reaction is avoided. Protonation is induced by HCl injection. The reaction in the thin DA coating layer generates a non-trivial evolution of the bubble radius with amplitude oscillations of the order of 10−3 of the bubble radius with persisting time of a few hundred seconds. Measurements are performed at different DA coverages of the bubble surface, always below the maximum coverage. Control experiments with non-coated bubble show no amplitude radius oscillations. Formation and stability of the DA monolayer are precisely monitored by measurements of the lowest-frequency bubble capillary mode. A possible interpretation of the experiments is given in terms of heat effects, vapor production and surface modification. Molecular Dynamics simulations provide a mechanistic understanding of surface effects triggered by the protonation reaction which promotes desorption of positively charged DA micelles. [Display omitted] [ABSTRACT FROM AUTHOR]

• hBN-based thermal regulation by adjusting its shift frequency is investigated. • Adjustable hyperbolic modes can couple and decouple with surface polaritons. • Regulation ratios reach 159.6 for hBN plates, and > 2 for SiC/hBN and G/hBN plates. Nanoscale thermal regulation plays a vital role in many applications, especially in highly-integrated electronics. In this study, we theoretically analyze the near-field radiation heat transfer within hBN-based planar systems, including bare hBN plates, SiC/hBN plates, graphene/hBN plates and Au/hBN plates. We predict that tailoring the shift frequency of phonon could alter the hyperbolic modes (HMs) of hBN, thus allowing for the coupling and decoupling of HMs with SPhPs of SiC and GSPPs of graphene. Therefore, the radiative heat flux in hBN-based systems except for Au/hBN plates can be greatly regulated, and the regulation ratio can reach 159.6 for bare hBN plates, and above 2 for SiC/hBN plates and for graphene/hBN plates. Results may facilitate understanding of the principles of hBN-based evanescent wave coupling and nanoscale thermal management. [ABSTRACT FROM AUTHOR]

Near-field thermophotovoltaics (NFTPV) is of great interest because it can achieve both high power density and high efficiency at medium to high temperature. One key to efficient photovoltaic conversion is an emitter that can selectively emit spectrum. Indium tin oxide (ITO) is considered as the emitter for NFTPV because its plasma frequency is tunable by simple technical means. However, as a typical degenerate semiconductor, the temperature dependence of its dielectric constant is often neglected in studying the performance of NFTPV. Therefore, we propose a NFTPV model considering the temperature-dependent property of ITO. By changing the applied voltage V, the vacuum gap d , and the emitter temperature T 1 , the performance of NFTPV with and without temperature dependence is compared and shows a significant difference. We find that the heat flux is always underestimated as well as the optimal efficiency is overestimated when the temperature dependence is not considered. At d = 10 nm and T 1 = 1000 K, the optimal efficiency is even overestimated by about 270%. Without considering the temperature dependence, the output power is overestimated at d < 20 nm, while the opposite is true at d ≥ 20 nm. We clarify the main reasons for these misjudgments at a small gap originate from the underestimation of the intensity of surface phonon polaritons (SPhPs) below the bandgap and the overestimation of the intensity of surface plasmon polaritons (SPPs) above the bandgap. The main factor affecting the two kinds of surface modes in near-field regime is that high temperatures lead to low electromagnetic local density of states (LDOS) for ITO emitter near the SPPs resonant frequency, but high LDOS in the ultralow frequencies. In a larger gap, it is attributed to the underestimation of the waveguide modes above the bandgap and the nearly-full-band propagation modes. Our work illustrates the necessity of considering temperature dependence, enriches the understanding of NFTPV, and facilitates the development of related applications. [ABSTRACT FROM AUTHOR]

• We derive the formula for radiative heat flux between dipole particles and a multilayer composed of the uniaxial medium. • The multilayered surface modes can be coupled to the particle resonance, enhancing heat flux between the particle and slab. • The phase change feature of VO2 allows the active control of the heat flux by changing the slab's temperature. • We address the role of multilayer parameters on the modulation effect. • We demonstrate that the multilayered structure can also actively tune the heat flux between the nanoparticles array and slab. We derive the formula for the near-field radiative heat flux between dipole particles and a multilayered slab composed of the uniaxial medium. Based on that, the multilayered structure consisting of SiC and VO 2 materials is applied to actively modulate the radiative heat transfer between nanoparticles and slab. Utilizing the modulation feature of the multilayer, surface modes from the multilayer can be strongly coupled to the particle resonance, greatly enhancing the heat flux between the particle and slab. The phase change feature of VO 2 allows the active control of multilayered surface modes by changing the slab's temperature, greatly tuning the heat flux. We address the role of multilayer parameters on the modulation effect. We also demonstrate that the multilayered structure can also actively tune the heat flux between the nanoparticle array and slab. [ABSTRACT FROM AUTHOR]

We present a theoretical study of the surface magnon-polaritons at an interface formed by vacuum and a gyromagnetic medium (that can be either ferromagnetic or antiferromagnetic), when there is a graphene layer deposited between the media at the interface and a magnetic field is applied perpendicular to the interface. The retarded-mode dispersion relations are calculated by considering a superposition of transverse magnetic and transversal electric electromagnetic waves in both media. Our results reveal the appearance of the surface magnon-polariton modes (with frequencies typically of a few GHz) that do not exist in the absence of graphene at the interface. Also, a typical magnon-polariton dispersion relation with damping is revealed, including a resonant frequency that depends on the applied magnetic field. The effects of varying the doping levels, which modify the Fermi energies in the graphene, and varying the perpendicular applied magnetic field are presented, revealing a strong influence exerted by the presence of graphene on the surface magnon-polariton modes. Other effects include the control of the slope of the dispersion curves (with respect to the in-plane wave vector) for the modes as the Fermi energies of the graphene sheet are changed and the distinctive localization properties for the emerging surface modes., (© 2023 IOP Publishing Ltd.)