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Transport in armchair graphene nanoribbons and in ordinary waveguides
摘要： We study dc and ac transport along armchair graphene nanoribbons using the k (cid:1) p spectrum and eigenfunctions and general linear-response expressions for the conductivities. Then, we contrast the results with those for transport along ordinary waveguides. In all cases, we assess the influence of elastic scattering by impurities, describe it quantitatively with a Drude-type contribution to the current previously not reported, and evaluate the corresponding relaxation time for long- and short-range impurity potentials. We show that this contribution dominates the response at very low frequencies. In both cases, the conductivities increase with the electron density and show cusps when new subbands start being occupied. As functions of the frequency, the conductivities in armchair graphene nanoribbons exhibit a much richer peak structure than in ordinary waveguides: in the former, intraband and interband transitions are allowed, whereas in the latter, only the intraband ones occur. This difference can be traced to that between the corresponding spectra and eigenfunctions.
关键词： transport,elastic scattering,armchair graphene nanoribbons,intraband and interband transitions,conductivities,relaxation time,Drude-type contribution
更新于2025-09-11 14:15:04
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Bound-to-continuum intraband transition properties in InAs/GaAs quantum dot superlattice solar cells
摘要： We studied the interband and intraband excitation densities and the polarization dependent photocurrent in InAs/GaAs quantum dot superlattice (QDSL) solar cells with a built-in electric field of 5 kV cm?1. An almost polarization-insensitive intraband transition was observed for normal incident light, whereas slight anisotropy in the intraband transition resulted from the mixing between the conduction and valence bands. Furthermore, saturable two-color photocurrent was observed in the p–i–n solar-cell device because of electron transport in the QDSL miniband.
关键词： intraband transition,polarization anisotropy,quantum dot superlattice,solar cells,InAs/GaAs
更新于2025-09-11 14:15:04
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A gauge-invariant formulation of interband and intraband currents in solids
摘要： Experiments and simulations in solid-state high harmonic generation often make use of the distinction between interband and intraband currents. These two contributions to the total current have been associated with qualitatively different processes as well as physically measurable signatures, for example, in the spectral phase of harmonic emission. However, it was recently argued [P. F?ldi, Phys. Rev. B 96, 035112 (2017)] that these quantities can depend on the gauge employed in calculations. Since physical quantities are expected to have gauge-independent values, this raises the question of whether the decomposition of the total current into interband and intraband contributions is physically meaningful or merely a feature of a particular mathematical representation of nature. In this article, we explore this apparent ambiguity. We show that a closely related issue arises when calculating instantaneous band populations. In both the case of inter/intraband currents and the case of instantaneous band populations, we propose definitions that are gauge invariant and thus allow these quantities to be calculated consistently in any gauge.
关键词： gauge invariance,solid-state,interband currents,band populations,intraband currents,high harmonic generation
更新于2025-09-09 09:28:46
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Anomalous carrier transport model for broadband infrared absorption in metals
摘要： We derive a model for accurately reproducing the broadband infrared optical response of common engineering metals. Here we use “broadband infrared” to refer to wavelengths beginning at 1 μm and extending to approximately 100 μm or more. The model generalizes the Drude theory to account for sources of anomalous intraband absorption. This is accomplished by modeling these sources as elements of disorder that introduce diffusive perturbations into the local ?eld. In the stationary setting, the memory kernel description of the ?eld relaxation leads to a fractional derivative with an order that corresponds to the memory decay strength. We demonstrate that this model is fully consistent with the Drude theory and that the semiclassical theory is recovered under requisite assumptions on the ?eld relaxation or radiative wavelength. The anomalous model component is shown to reproduce empirically observed anomalous absorption that has been traditionally corrected by models possessing empirical components that have not been formally derived. Results are presented for several common metals for which the proposed model accurately reproduces the data over the entire modeled bandwidth. A comparative analysis con?rms that the proposed model represents a robust, high ?delity alternative to previously proposed models that do not capture the observed physical response over the extended infrared range.
关键词： broadband infrared,anomalous intraband absorption,fractional derivative,Drude theory,memory kernel
更新于2025-09-04 15:30:14
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Ultrathin Conductor Enabling Efficient IR Light CO2 Reduction
摘要： Concurrent transformation of carbon dioxide and water into hydrocarbons and oxygen by low-photonic-energy IR light still represents a huge challenge. Here, we design an ultrathin conductor system, in which the special partially occupied band serves as the mediator to simultaneously guarantee IR light harvesting and satisfied band-edge positions, while the ultrathin configuration improves charge separation rates and surface redox kinetics. Taking the low cost and earth abundant CuS as an example, we first fabricate ultrathin CuS layers, where temperature-dependent resistivities, valence-band spectrum and theoretical calculation affirm their metallic nature. Synchrotron-radiation photoelectron and ultraviolet-visible-near infrared spectra unveil metallic CuS atomic layers could realize a new cooperative intraband-interband transition under IR light irradiation, where the generated electrons and holes could simultaneously involve the carbon dioxide reduction and water oxidation reactions. As a result, CuS atomic layers exhibit nearly 100% selective CO production with an evolution rate of 14.5 μmol g-1 h-1 under IR light irradiation, while the catalytic performance shows no obvious decay after 96 h test. Briefly, benefiting from ultrahigh conductivity and unique partially occupied band, the abundant conductor materials such as conducting metal sulfides and metal nitrides hold great promise for applications as effective IR light responsive photocatalysts.
关键词： intraband-interband transition,ultrathin,CO2 reduction,conductor,IR light
更新于2025-09-04 15:30:14