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91.
In two dimensional electron systems with Coulomb or dipolar interactions, a direct transition, whether first or second order, from a liquid to a crystalline state is forbidden. As a result, between these phases there must be other (micro-emulsion) phases which can be viewed as a meso-scale mixture of the liquid and crystalline phases. We investigate the transport properties of these new electronic phases and present arguments that they are responsible for the various transport anomalies that have been seen in experiments on the strongly correlated 2DEG in high mobility semiconductor devices with low electron densities. 相似文献
92.
Farjadpour A Roundy D Rodriguez A Ibanescu M Bermel P Joannopoulos JD Johnson SG Burr GW 《Optics letters》2006,31(20):2972-2974
Finite-difference time-domain (FDTD) methods suffer from reduced accuracy when modeling discontinuous dielectric materials, due to the inhererent discretization (pixelization). We show that accuracy can be significantly improved by using a subpixel smoothing of the dielectric function, but only if the smoothing scheme is properly designed. We develop such a scheme based on a simple criterion taken from perturbation theory and compare it with other published FDTD smoothing methods. In addition to consistently achieving the smallest errors, our scheme is the only one that attains quadratic convergence with resolution for arbitrarily sloped interfaces. Finally, we discuss additional difficulties that arise for sharp dielectric corners. 相似文献
93.
Alexander Bass Seth Putterman Barry Merriman Steven J. Ruuth 《Journal of computational physics》2008,227(3):2118-2129
We propose a symmetry reduction technique whereby molecular dynamics (MD) simulations for spherically symmetric gas bubbles can be accelerated. Results for an imploding Xenon bubble containing 50 million particles—the smallest measured sonoluminescing system—are presented. 相似文献
94.
Sebastiaan van Dijken Xavier Fain Steven M. Watts Kentaro Nakajima J. M. D. Coey 《Journal of magnetism and magnetic materials》2004,280(2-3):322-326
A detailed study of the in-plane magnetotransport properties of spin valves with one and two Fe3O4 electrodes is presented. Fe3O4/Au/Fe3O4 spin valves exhibit a clear anisotropic magnetoresistance in small magnetic fields but no giant magnetoresistance (GMR). The absence of GMR in these structures is due to simultaneous magnetization reversal in the two Fe3O4 layers. By contrast, a negative GMR effect is measured on Fe3O4/Au/Fe spin valves. The negative GMR is attributed to an electron spin scattering asymmetry at the Fe3O4/Au interface or an induced spin scattering asymmetry in the Au interfacial layers. 相似文献
95.
Complex random states have the statistical properties of the Gaussian and circular unitary ensemble eigenstates of random matrix theory. Even though their components are correlated by the normalization constraint, it is nevertheless possible to derive compact analytic formulas for their extreme values' statistical properties for all dimensionalities. The maximum intensity result slowly approaches the Gumbel distribution even though the variables are bounded, whereas the minimum intensity result rapidly approaches the Weibull distribution. Since random matrix theory is conjectured to be applicable to chaotic quantum systems, we calculate the extreme eigenfunction statistics for the standard map with parameters at which its classical map is fully chaotic. The statistical behaviors are consistent with the finite-N formulas. 相似文献
96.
Magnetic edge-state excitons in zigzag graphene nanoribbons 总被引:1,自引:0,他引:1
We present first-principles calculations of the optical properties of zigzag-edged graphene nanoribbons (ZGNRs) employing the GW-Bethe-Salpeter equation approach with the spin interaction included. Optical response of the ZGNRs is found to be dominated by magnetic edge-state-derived excitons with large binding energy. The absorption spectrum is composed of a characteristic series of exciton states, providing a possible signature for identifying the ZGNRs. The edge-state excitons are charge-transfer excitations with the excited electron and hole located on opposite edges; they moreover induce a spin transfer across the ribbon, resulting in a photoreduction of the magnetic ordering. These novel characteristics are potentially useful in the applications. 相似文献
97.
Simultaneous detection of ultraviolet and infrared radiation in a single GaN/GaAlN heterojunction 总被引:1,自引:0,他引:1
Jayasinghe RC Ariyawansa G Dietz N Perera AG Matsik SG Yu HB Ferguson IT Bezinger A Laframboise SR Buchanan M Liu HC 《Optics letters》2008,33(21):2422-2424
Results are presented for a dual-band detector that simultaneously detects UV radiation in the 250-360 nm and IR radiation in the 5-14 microm regions with near zero spectral cross talk. In this detector having separate UV- and IR-active regions with three contacts (one common contact for both regions) allows the separation of the UV and IR generated photocurrent components, identifying the relative strength of each component. This will be an important development in UV-IR dual-band applications such as fire-flame detection, solar astronomy, and military sensing, eliminating the difficulties of employing several individual detectors with separate electronics-cooling mechanisms. 相似文献
98.
Shub DE Durlach NI Colburn HS 《The Journal of the Acoustical Society of America》2008,123(6):4421-4433
The ability to make judgments about the stimulus at one ear when a stimulus is simultaneously presented to the other ear was tested. Specifically, subjects discriminated the level of a 600 Hz target tone presented at the left ear while an identical-frequency distractor was simultaneously presented at the other ear. When there was no distractor, threshold was 0.7 dB. Threshold increased to 1.1 dB when a distractor with a fixed phase and level was introduced contra-aurally to the target. Further increases in threshold were observed when an across-presentation variability was introduced into the distractor phase (threshold of 1.6 dB) or level (threshold of 5.8 dB). When both the distractor level and phase varied, the largest threshold of 7.3 dB was obtained. These increases in threshold cannot be predicted by common binaural models, which assume that a target stimulus at one ear can be processed without interference from the stimulus at the nontarget ear. The measured thresholds are consistent with a model that utilizes two binaural dimensions that roughly correspond to the loudness and the position of a fused binaural image. The results show that, with binaurally fused tonal stimuli, subjects are unable to listen to one ear. 相似文献
99.
Steven Verlinden Tatiana Woller Prof. Frank De Proft Prof. Guido Verniest Prof. Mercedes Alonso 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(11):2840-2851
The importance of axially chiral biaryls has risen steeply in the recent decades. This structural motif proved to be successful in catalytic asymmetric synthesis and the configuration of the biaryl axis is decisive for the biological activity. A new approach for the atroposelective synthesis of biaryls would be through a cycloaddition between an enantiopure phenyl-substituted thiophene S-oxide and an alkyne. Importantly, the chiral center of the thiophene S-oxide needs to be stable enough to avoid pyramidal inversion during the cycloaddition. Considering that the racemization of thiophene monoxides has been scarcely investigated so far, we perform a thorough quantum chemical study on the inversion barriers of a large number of chiral thiophene S-oxide derivatives. Our main goal is to identify substitution patterns leading to stable atropisomers at room temperature. Appealingly, the role of stereoelectronic effects and the position of the substituents as well as the importance of aromaticity on the pyramidal inversion barrier are elucidated for the first time. 相似文献
100.
Dr. James Jennings Dr. Erik J. Cornel Dr. Matthew J. Derry Dr. Deborah L. Beattie Dr. Matthew J. Rymaruk Oliver J. Deane Prof. Anthony J. Ryan Prof. Steven P. Armes 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(27):10940-10945
Polymerization-induced self-assembly (PISA) enables the scalable synthesis of functional block copolymer nanoparticles with various morphologies. Herein we exploit this versatile technique to produce so-called “high χ–low N” diblock copolymers that undergo nanoscale phase separation in the solid state to produce sub-10 nm surface features. By varying the degree of polymerization of the stabilizer and core-forming blocks, PISA provides rapid access to a wide range of diblock copolymers, and enables fundamental thermodynamic parameters to be determined. In addition, the pre-organization of copolymer chains within sterically-stabilized nanoparticles that occurs during PISA leads to enhanced phase separation relative to that achieved using solution-cast molecularly-dissolved copolymer chains. 相似文献