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Optical, charge transport and magnetic properties of palladium retrieved from photometric measurements: approaching the quantum mechanics background
摘要： A parametric Drude–Lorentz (DL) model is used to describe the spectral variation of the dielectric functions of bulk palladium samples at low and room temperature. In addition to the contribution of conduction electrons, the contribution of holes is also explicitly accounted for in the model. A simulated annealing method is applied to obtain the optimized values of the parameters involved in the model: volume plasma frequency of conduction electrons, high frequency dielectric constant, collision frequency of holes and corresponding relaxation time, and two additional parameters from which the effective mass of holes and collision frequency of conduction electrons are evaluated. Oscillatior strengths, resonance frequencies, and widths entering in the Lorentz contribution to the dielectric function are also optimized. Renormalization of the oscillator strengths requires the introduction of a new parameter in the context of the DL model: the ratio between number density of conduction electrons and number density of metal atoms, whose optimized value ?ts very well with its evaluation from band structure calculations and from independent measurements. Inclusion of this parameter in the framework allows us to evaluate additional quantities related to the charge-carrier transport: average effective masses, Fermi energies and electronic densities of states at the corresponding Fermi energies, intrinsic electrical resistivity, intrinsic mean free paths, heat capacities, mobilities, as well as paramagnetic and diamagnetic susceptibilities, for both electrons and holes. The optimized resonance frequencies are compared with energy differences between plausible interband transitions, in accordance with reported band structure diagrams and with our own band structure obtained from density functional theory calculations.
关键词： Drude–Lorentz model,palladium,density functional theory,simulated annealing,metal thin ?lms
更新于2025-11-14 15:19:41
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Fundamentals and Applications of Nanophotonics || A dynamical, classical oscillator model for linear and nonlinear optics
摘要： In this chapter we will build and develop a self-consistent, classical oscillator model to describe linear and nonlinear optical interactions like refraction and frequency conversion in both centrosymmetric and noncentrosymmetric materials. In addition to being quite ubiquitous in all of physics, the classical oscillator model of matter is an enormously pedagogical tool that serves as a natural springboard to the description and understanding of quantum systems and leads to a rather detailed portrayal of all the dynamical factors that contribute to most linear and nonlinear optical phenomena. The method is endowed with causality as well as a natural degree of self-consistency that includes linear and nonlinear material dispersions, elements that are usually necessary to understand many of the subtleties of the interaction of light with matter. By way of examples, using this classical approach we will examine harmonic generation in bulk materials and in metal-based nanostructures. In centrosymmetric materials like metals (materials composed of molecules that lack a center of symmetry), second harmonic generation (SHG) arises mostly from nearly free, conduction electrons (nearly free because they are con?ned by the metal walls) and is due to a combination of spatial symmetry breaking (interfaces), the magnetic portion of the Lorentz force, and, to a lesser extent, the interaction of third harmonic (TH) and pump photons. By the same token, the third order nonlinearity (c(3)) gives rise to most of the TH signal, while to a small degree the interaction of pump and SH photons also produces cascaded, TH photons. The classical oscillator model will be pivotal in these systems as well, where a combination of free (Drude) and bound (Lorentz) electrons suf?ces to describe most linear and nonlinear optical phenomena.
关键词： Lorentz model,centrosymmetric materials,noncentrosymmetric materials,classical oscillator model,harmonic generation,linear and nonlinear optics,Drude model
更新于2025-09-16 10:30:52
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Fractional model of the dielectric dispersion
摘要： This work deals with the generalization of the Lorentz model. It is made using the Caputo fractional derivative of order 0 < γ ≤ 1 in the frequency domain. The fractional complex dielectric function, index of refraction, re?ectance, electric susceptibility were obtained. It is shown that all of them depend not only on the frequency of applied ?eld, but also on the fractional order of the di?erential equation 0 < γ ≤ 1. This opens the possibility to describe more accurately the experimental results in complex systems. The ordinary results are obtained when γ = 1.
关键词： Lorentz model,Fractional calculus,Caputo derivative
更新于2025-09-09 09:28:46