Unlike conventional optics, plasmonics enables unrivalled concentration of optical energy well beyond the diffraction limit of light. However, a significant part of this energy is dissipated as heat. Plasmonic losses present a major hurdle in the development of plasmonic devices and circuits that can compete with other mature technologies. Until recently, they have largely kept the use of plasmonics to a few niche areas where loss is not a key factor, such as surface enhanced Raman scattering and biochemical sensing. Here, we discuss the origin of plasmonic losses and various approaches to either minimize or mitigate them based on understanding of fundamental processes underlying surface plasmon modes excitation and decay. Along with the ongoing effort to find and synthesize better plasmonic materials, optical designs that modify the optical powerflow through plasmonic nanostructures can help in reducing both radiative damping and dissipative losses of surface plasmons. Another strategy relies on the development of hybrid photonicplasmonic devices by coupling plasmonic nanostructures to resonant optical elements. Hybrid integration not only helps to reduce dissipative losses and radiative damping of surface plasmons, but also makes possible passive radiative cooling of nano-devices. Finally, we review emerging applications of thermoplasmonics that leverage Ohmic losses to achieve new enhanced functionalities. The most successful commercialized example of a loss-enabled novel application of plasmonics is heat-assisted magnetic recording. Other promising technological directions include thermal emission manipulation, cancer therapy, nanofabrication, nano-manipulation, plasmon-enabled material spectroscopy and thermo-catalysis, and solar water treatment. OCIS codes: (240.6680) Surface plasmons; (230.3990) Micro-optical devices; (130.6010) Sensors; (350.5340) Photothermal effects; (290.6815) Thermal emission; (240.6675) Surface photoemission and photoelectron spectroscopy; (350.6670) Surface photochemistry.
Through first-principles calculations, the phonon-limited transport properties of cubic boron-V compounds (BP, BAs and BSb) are studied. We find that the high optical phonon frequency in these compounds leads to the substantial suppression of polar scattering and the reduction of inter-valley transition mediated by large-wavevector optical phonons, both of which significantly facilitate charge transport. We also discover that BAs simultaneously has a high hole mobility (2110 cm 2 /V-s) and electron mobility (1400 cm 2 /V-s) at room temperature, which is rare in semiconductors. Our findings present a new insight in searching high mobility polar semiconductors, and point to BAs as a promising material for electronic and photovoltaic devices in addition to its predicted high thermal conductivity.
Harnessing the oxidation−reduction reaction between aluminum and water is an attractive option for hydrogen generation and storage. Using liquid metals as a method of circumventing aluminum's native oxide layer has been gaining popularity, yet the underlying reaction mechanism and various effects on hydrogen generation remain elusive. This article reports the investigation of liquid-metal-activated aluminum that has been doped with commonly employed alloying elements. We observe that the eutectic Ga−In penetrates through subgrain boundaries in aluminum, providing experimental evidence that the eutectic permeates as a line dislocation front. We also demonstrate the opposing effects that magnesium and silicon alloying elements have on the hydrogen-generating properties of liquid-metal-activated commercial aluminum alloys. Compared to pure aluminum, the addition of 0.6 wt % silicon to aluminum gives rise to significantly higher reaction rates and hydrogen yields (+20%). The addition of 1 wt % magnesium to aluminum significantly lowers the rate and yield, especially following 72 h of eutectic Ga−In permeation (−30%). When both magnesium and silicon are present in aluminum such that intermetallic particles are formed like in the commercial alloy AA6061, the rate and extent of the aluminum−water reaction are highly dependent on permeation time. After 96 h of permeation, Al + Mg, Si produces the same amount of hydrogen as pure aluminum produces following only 48 h of permeation. These experimental observations do not agree well with historical studies based on pure corrosion of aluminum, indicating that the reaction mechanism involving eutectic Ga−In is more complex and hence requires additional investigations to understand. Using these discoveries, we can now better predict the reaction rate of the aluminum with water when considering Mg-doped and/or Si-doped scrap aluminum as a fuel source, giving rise to more applications in which aluminum can be harnessed as a hydrogen production and storage technology.
Despite the established knowledge that crystal dislocations can affect a material's superconducting properties, the exact mechanism of the electron-dislocation interaction in a dislocated superconductor has long been missing. Being a type of defect, dislocations are expected to decrease a material's superconducting transition temperature (T) by breaking the coherence. Yet experimentally, even in isotropic type I superconductors, dislocations can either decrease, increase, or have little influence on T. These experimental findings have yet to be understood. Although the anisotropic pairing in dirty superconductors has explained impurity-induced T reduction, no quantitative agreement has been reached in the case a dislocation given its complexity. In this study, by generalizing the one-dimensional quantized dislocation field to three dimensions, we reveal that there are indeed two distinct types of electron-dislocation interactions. Besides the usual electron-dislocation potential scattering, there is another interaction driving an effective attraction between electrons that is caused by dislons, which are quantized modes of a dislocation. The role of dislocations to superconductivity is thus clarified as the competition between the classical and quantum effects, showing excellent agreement with existing experimental data. In particular, the existence of both classical and quantum effects provides a plausible explanation for the illusive origin of dislocation-induced superconductivity in semiconducting PbS/PbTe superlattice nanostructures. A quantitative criterion has been derived, in which a dislocated superconductor with low elastic moduli and small electron effective mass and in a confined environment is inclined to enhance T. This provides a new pathway for engineering a material's superconducting properties by using dislocations as an additional degree of freedom.
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