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Register a new userIntroduction to the Physics of Silicene and other 2D Materials
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This concise book offers an essential introduction and reference guide for the many newcomers to the field of physics of elemental 2D materials. Silicene and related materials are currently among the most actively studied materials, especially following the first experimental synthesis on substrates in 2012. Accordingly, this primer introduces and reviews the most crucial developments regarding silicene from both theoretical and experimental perspectives. At the same time the reader is guided through the extensive body of relevant foundational literature. The text starts with a brief history of silicene, followed by a comparison of the bonding nature in silicon versus carbon atoms. Here, a simple but robust framework is established to help the reader follow the concepts presented throughout the book. The book then presents the atomic and electronic structure of free-standing silicene, followed by an account of the experimental realization of silicene on substrates. This topic is subsequently developed further to discuss various reconstructions that silicene acquires due to interactions with the substrate and how such effects are mirrored in the electronic properties. Next the book examines the dumbbell structure that is the key to understanding the growth mechanism and atomic structure of multilayer silicene. Last but not least, it addresses similar effects in other elemental 2D materials from group IV (germanene, stanane), group V (phosphorene) and group III (borophene), as well as transition metal dichalcogenides and other compositions, so as to provide a general comparative overview of their electronic properties.
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We present a short pedagogical introduction to the physics of Dirac materials, restricted to graphene and two- dimensional topological insulators. We start with a brief reminder of the Dirac and Weyl equations in the particle physics context. Turning to condensed matter systems, semimetallic graphene and various Dirac insulators are introduced, including the Haldane and the Kane-Mele topological insulators. We also discuss briefly experimental realizations in materials with strong spin-orbit coupling.
Silicene, a monolayer of silicon atoms tightly packed into a two-dimensional honeycomb lattice, is the challenging hypothetical reflection in the silicon realm of graphene, a one-atom thick graphite sheet, presently the hottest material in condensed matter physics. If existing, it would also reveal a cornucopia of new physics and potential applications. Here, we reveal the epitaxial growth of silicene stripes self-aligned in a massively parallel array on the anisotropic silver (110) surface. This crucial step in the silicene gold rush could give a new kick to silicon on the electronics road-map and opens the most promising route towards wide-ranging applications. A hint of superconductivity in these silicene stripes poses intriguing questions related to the delicate interplay between paired correlated fermions, massless Dirac fermions and bosonic quasi-particules in low dimensions.
Collective modes of doped two-dimensional crystalline materials, namely graphene, MoS$_2$ and phosphorene, both monolayer and bilayer structures, are explored using the density functional theory simulations together with the random phase approximation. The many-body dielectric functions of the materials are calculated using an {it ab initio} based model involving material-realistic physical properties. Having calculated the electron energy-loss, we calculate the collective modes of each material considering the in-phase and out-of-phase modes for bilayer structures. Furthermore, owing to many band structures and intreband transitions, we also find high-energy excitations in the systems. We explain that the material-specific dielectric function considering the polarizability of the crystalline material such as MoS$_2$ are needed to obtain realistic plasmon dispersions. For each material studied here, we find different collective modes and describe their physical origins.
First-principles calculations have become a powerful tool to exclude the Edisonian approach in search of novel 2d materials. However, no universal first-principles criteria to examine the realizability of hypothetical 2d materials have been established in the literature yet. Because of this, and since the calculations are always performed in an artificial simulation environment, one can unintentionally study compounds that do not exist in the experiments. Although investigations of physics and chemistry of unrealizable materials can provide some fundamental knowledge, the discussion of their applications can mislead experimentalists for years and increase the gap between experimental and theoretical research. By analyzing energy convex hull, phonon spectra, and structure evolution during ab initio molecular dynamics simulations for a range of synthesized and recently proposed 2d materials, we construct energy, phonon, and dynamic stability filters which need to be satisfied before proposing novel 2d compounds. We demonstrate the power of the suggested filters for several selected 2d systems, revealing that some of them cannot be ever realized experimentally.
A method was developed to calculate the free energy of 2D materials on substrates and was demonstrated by the system of graphene and {gamma}-graphyne on copper substrate. The method works at least 3 orders faster than state-of-the-art algorithms, and the accuracy was tested by molecular dynamics simulations, showing that the precision for calculations of the internal energy achieves up to 0.03% in a temperature range from 100 to 1300K. As expected, the calculated the free energy of a graphene sheet on Cu (111) or Ni (111) surface in a temperature range up to 3000K is always smaller than the one of a {gamma}-graphyne sheet with the same number of C atoms, which is consistent with the fact that growth of graphene on the substrates is much easier than {gamma}-graphyne.
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