Dissipative Quantum Mechanics of Nanostructures: Electron Transport, Fluctuations, and Interactions
Continuing miniaturization of electronic devices, together with the quickly growing number of nanotechnological applications, demands a profound understanding of the underlying physics. Most of the fundamental problems of modern condensed matter physics involve various aspects of quantum transport and fluctuation phenomena at the nanoscale. In nanostructures, electrons are usually confined to a limited volume and interact with each other and lattice ions, simultaneously suffering multiple scattering events on impurities, barriers, surface imperfections, and other defects. Electron interaction with other degrees of freedom generally yields two major consequences, quantum dissipation and quantum decoherence. In other words, electrons can lose their energy and ability for quantum interference even at very low temperatures. These two different, but related, processes are at the heart of all quantum phenomena discussed in this book.This book presents copious details to facilitate the understanding of the basic physics behind a result and the learning to technically reproduce the result without delving into extra literature. The book subtly balances the description of theoretical methods and techniques and the display of the rich landscape of the physical phenomena that can be accessed by these methods. It is useful for a broad readership ranging from master's and PhD students to postdocs and senior researchers.
We consider the optical conductivity of a clean two-dimensional metal near a quantum spin-density-wave transition. Critical magnetic fluctuations are known to destroy fermionic coherence at “hot spots” of the Fermi surface but coherent quasiparticles survive in the rest of the Fermi surface. A large part of the Fermi surface is not really “cold” but rather “lukewarm” in a sense that coherent quasiparticles in that part survive but are strongly renormalized compared to the noninteracting case. We discuss the self-energy of lukewarm fermions and their contribution to the optical conductivity σ(), focusing specifically on scattering off composite bosons made of two critical magnetic fluctuations. Recent study [S. A. Hartnoll et al., Phys. Rev. B 84, 125115 (2011)] found that composite scattering gives the strongest contribution to the self-energy of lukewarm fermions and suggested that this may give rise to a non-Fermi-liquid behavior of the optical conductivity at the lowest frequencies. We show that the most singular term in the conductivity coming from self-energy insertions into the conductivity bubble σ(Omega) ∝ ln^3(Omega) /(Omega)^(1/3) is canceled out by the vertex-correction and Aslamazov-Larkin diagrams. However, the cancellation does not hold beyond logarithmic accuracy, and the remaining conductivity still diverges as 1/(Omega)^(1/3). We further argue that the 1/(Omega)^(1/3) behavior holds only at asymptotically low frequencies, well inside the frequency range affected by superconductivity. At larger Omega, up to frequencies above the Fermi energy, σ(Omega) scales as 1/(Omega), which is reminiscent of the behavior observed in the superconducting cuprates.
Semiconductor nanostructures: electronic, optical properties, formation methods
International Conference on Micro- and Nano-Electronics 2016
We report room temperature injection lasing in the yellow–orange spectral range (599–605 nm) in (AlxGa1–x)0.5In0.5P–GaAs diodes with 4 layers of tensilestrained InyGa1–yP quantum dot-like insertions. The wafers were grown by metal–organic vapor phase epitaxy side-by-side on (811), (211) and (322) GaAs substrates tilted towards the <111> direction with respect to the (100) surface. Four sheets of GaP-rich quantum barrier insertions were applied to suppress leakage of non-equilibrium electrons from the gain medium. Laser diodes having a threshold current densities of ~7–10 kA/cm2 at room temperature were realized for both (211) and (322) surface orientations at cavity lengths of ~1mm. Emission wavelength at room temperature ~600 nm is shorter by ~8 nm than previously reported. As an opposite example, the devices grown on (811) GaAs substrates did not show lasing at room temperature.
This volume contains the papers presented at the session "Data Science" within the V International Conference on Information Technology and Nanotechnology (ITNT-2019). The conference was held in Samara, Russia, during May 21-24, 2019 (itnt-conf.org). The conference is a forum for leading researchers from all over the world aimed to discuss the latest advances in the basic and applied research in the field of Information Technology and Nanotechnology. It is also aimed to attract young people to advanced scientific research and share the latest trends in training and research programs for future ITNT specialists . In addition to the session "Data Science", ITNT-2019 also included three other sessions: "Computer Optics and Nanophotonics", "Image Processing and Earth Remote Sensing" and "Mathematical Modeling of Physico-Technical Processes and Systems". The whole forum brought together more than 450 scientists from United Kindom, Japan, Switzerland, Iran, Poland, Bulgaria, Finland, China, Kazakhstan and Russia, as well as representatives of global high-tech corporations, developers of modern electronics – Huawei, Nvidia, Intel, and Azimuth Photonics, and more than 60 cities in the world. 436 talks enabled discussion on a wide range of topics. The topics of the session "Data Science" were grouped into the following key directions: Data Mining (Big data, Systems and platforms, Methods); Machine Learning (Neural networks, Statistical methods, Feature-based classification, Applications); Security, Cryptography (Cryptosystems design and analysis, Mathematical and algorithmic aspects, Efficient implementations of algorithms, Network security); High Performance Computing (Parallel programming models and languages, Highperformance implementations, Complex systems simulation).
The swelling of a poly (methyl methacrylate) in supercritical carbon dioxide was studied by means of full atomistic classical molecular dynamics simulation. In order to characterize the polymer swelling, we calculated various properties related to the density, structure, and dynamics of polymer chains as a function of the simulation time, temperature, and pressure. In addition, we compared the properties of the macromolecular chains in supercritical CO2 with the properties of the corresponding bulk system at the same temperature and atmospheric pressure. It was shown that diffusion of CO2 molecules into the polymer led to a significant increase in the chain mobility and distances between them. Analysis of diffusion coefficients of CO2 molecules inside and outside the poly(methyl methacrylate) sample has shown that carbon dioxide actively interacts with the functional groups of poly (methyl methacrylate). Joint analysis of the radial distribution functions obtained from classical molecular dynamics and of the averaging interatomic distances from Car-Parrinello molecular dynamics allows us to make a conclusion about the possibility of formation of weak hydrogen bonds between the carbon dioxide oxygen atom and the hydrogen atoms of the polymer methyl groups.
We report the first experimental evidence for the mitogenic action of cerium(IV) oxide and cerium(III) fluoride nanoparticles (CONs and CFNs) on the regeneration of a whole organism – freshwater flatworms Schmidtea mediterranea (planarian). Both types of cerium-containing nanoparticles are shown to be a highly potent mitogen for planaria. Both CONs and CFNs, in micro- and nanomolar concentrations, markedly accelerate planarian blastema growth, due to the enhancement of cellular proliferation, causing an increase in the mitotic index and in the quantity of blastema cells in regenerating planaria. CONs provided maximum activity at concentrations which were two orders of magnitude lower than those for CeF3. The valence state of cerium in cerium-containing nanoparticles plays a significant role in the planarian regeneration mechanism: CeO2 nanoparticles containing predominantly Ce4+ species presumably scavenge wound induced reactive oxygen species and moderately activate gene expression processes, while the regenerative action of CeF3 nanoparticles containing only Ce3+ species is manifested in the pronounced expression of the genes involved in cell division, differentiation and migration. This is the first report on the effect of cerium-containing nanoparticles on tissue regeneration in vivo, further revealing the mechanisms of their biological action, which enhances the possibility of their use in cellular technologies.
This volume presents new results in the study and optimization of information transmission models in telecommunication networks using different approaches, mainly based on theiries of queueing systems and queueing networks .
The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.