American Institute of Physics
About: AIP Advances is an academic journal published by American Institute of Physics. The journal publishes majorly in the area(s): Materials science & Magnetization. It has an ISSN identifier of 2158-3226. It is also open access. Over the lifetime, 13545 publications have been published receiving 118511 citations. The journal is also known as: American Institute of Physics advances.
TL;DR: The design, verification and performance of MUMAX3, an open-source GPU-accelerated micromagnetic simulation program that solves the time- and space dependent magnetization evolution in nano- to micro scale magnets using a finite-difference discretization is reported on.
Abstract: We report on the design, verification and performance of MUMAX3, an open-source GPU-accelerated micromagnetic simulation program. This software solves the time- and space dependent magnetization evolution in nano- to micro scale magnets using a finite-difference discretization. Its high performance and low memory requirements allow for large-scale simulations to be performed in limited time and on inexpensive hardware. We verified each part of the software by comparing results to analytical values where available and to micromagnetic standard problems. MUMAX3 also offers specific extensions like MFM image generation, moving simulation window, edge charge removal and material grains.
TL;DR: In this paper, it is shown that the high wavenumber "bump" can be resolved into the conventional 2D band and several defect activated peaks such as G*, D+D+D′ and 2D′.
Abstract: Graphene sheets that are now routinely obtained by the exfoliation/reduction of graphite oxide exhibit Raman spectra unlike traditional graphene systems. The general attributes of the Raman spectra of these ‘wrinkled graphene’ are first reaffirmed by evaluating the spectra of samples prepared by seven different exfoliation-reduction methods. These graphene sheets exhibit highly broadened D and G Raman bands and in addition, have a modulated bump in place of the conventional 2D (G′) band. It is shown that the high wavenumber ‘bump’ can be resolved into the conventional 2D band and several defect activated peaks such as G*, D+D′ and 2D′. The broad G band could also be deconvoluted into the actual G band and the D′ band, thereby attributing the broadening in the G band to the presence of this defect activated band. Two additional modes, named as D* at 1190 cm-1 and D** at ∼1500 cm-1 could be identified. These peculiar features in the Raman spectrum of ‘graphene’ are attributed to the highly disordered and wrinkled (defective) morphology of the sheets. The affect of defects are further augmented due to the finite crystallite size of these graphene sheets. The dispersion in the band positions and peak intensities with respect to the laser energy are also demonstrated.
TL;DR: In this article, the uncertainty of the band-to-band absorption coefficient of crystalline silicon was analyzed using the Guide to the expression of uncertainty in measurement (GUM) as well as an extensive characterization of the measurement setups.
Abstract: We analyze the uncertainty of the coefficient of band-to-band absorption of crystalline silicon. For this purpose, we determine the absorption coefficient at room temperature (295 K) in the wavelength range from 250 to 1450 nm using four different measurement methods. The data presented in this work derive from spectroscopic ellipsometry, measurements of reflectance and transmittance, spectrally resolved luminescence measurements and spectral responsivity measurements. A systematic measurement uncertainty analysis based on the Guide to the expression of uncertainty in measurement (GUM) as well as an extensive characterization of the measurement setups are carried out for all methods. We determine relative uncertainties of the absorption coefficient of 0.4% at 250 nm, 11% at 600 nm, 1.4% at 1000 nm, 12% at 1200 nm and 180% at 1450 nm. The data are consolidated by intercomparison of results obtained at different institutions and using different measurement approaches.
TL;DR: In this article, a modified Hummers method with different mass ratios of KMnO4 to graphite was used for the removal of few-layer (1-3 layers), multi-layer and thick-layer (>10 layers) graphene oxide (GO) dispersions.
Abstract: Dispersions of few-layer (1-3 layers), multi-layer (4-10 layers) and thick-layer (>10 layers) graphene oxide (GO) were prepared by a modified Hummers method with different mass ratios of KMnO4 to graphite Ultraviolet-visible (UV-vis) spectroscopic data show that few-layer GO dispersions can be distinguished from multi- and thick-layer dispersions by a more intense peak at 230 nm Atomic force microscopy (AFM) images of few-layer GO contain a single peak, those of multi-layer GO exhibit a shoulder and those of thick-layer GO do not contain a peak or shoulder These findings allow qualitative analysis of GO dispersions X-ray photoelectron spectra (XPS) show that the change of UV-vis absorption intensity of GO is caused by a conjugative effect related to chromophore aggregation that influences the π-π* plasmon peak
TL;DR: The Lindblad master equation as discussed by the authors is the most general generator of Markovian dynamics in quantum systems, and its derivation and methods of resolution can be found in this paper.
Abstract: The theory of open quantum systems is one of the most essential tools for the development of quantum technologies. Furthermore, the Lindblad (or Gorini-Kossakowski-Sudarshan-Lindblad) master equation plays a key role as it is the most general generator of Markovian dynamics in quantum systems. In this paper, we present this equation together with its derivation and methods of resolution. The presentation tries to be as self-contained and straightforward as possible to be useful to readers with no previous knowledge of this field.