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Twistronics
Twistronics (from ''twist'' and ''electronics'') is the study of how the angle (the twist) between layers of two-dimensional materials can change their electrical properties. Materials such as bilayer graphene have been shown to have vastly different electronic behavior, ranging from non-conductive to superconductive, that depends sensitively on the angle between the layers. The term was first introduced by the research group of Efthimios Kaxiras at Harvard University in their theoretical treatment of graphene superlattices. History In 2007, National University of Singapore physicist Antonio Castro Neto hypothesized that pressing two misaligned graphene sheets together might yield new electrical properties, and separately proposed that graphene might offer a route to superconductivity, but he did not combine the two ideas. In 2010 researchers from Universidad Técnica Federico Santa María in Chile found that for a certain angle close to 1 degree the band of the electronic st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterostrain
The term heterostrain was proposed in 2018 in the context of materials science to simplify the designation of possible strain situations in van der Waals heterostructures where two (or more) two-dimensional materials are stacked on top of each other. These layers can experience the same deformation (homostrain) or different deformations (heterostrain). In addition to twist, heterostrain can have important consequences on the electronic and optical properties of the resulting structure. As such, the control of heterostrain is emerging as a sub-field of straintronics in which the properties of 2D materials are controlled by strain. Etymology Heterostrain is constructed from the Greek prefix hetero- (different) and the noun strain. It means that the two layers constituting the structure are subject to different strains. This is in contrast with homostrain in which the two layers as subject to the same strain. Heterostrain is designated as "relative strain" by some authors. Mani ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yuan Cao
Yuan Cao () is a Chinese physicist. His research is focused on the properties of two-dimensional materials. He discovered that a stack of two sheets of graphene, cooled to 1.7 kelvins, K, could act as a superconductor or as an insulator when exposed to an electric field. In 2018, ''Nature'' chose him as one of 10 people who mattered that year in science, calling him a "graphene wrangler". Cao was born in Chengdu in 1996, and he attended Shenzhen Yaohua Experimental School starting in 2007. In 2010 he got into the Special Class for the Gifted Young at the University of Science and Technology of China. In 2014 he started graduate school at Massachusetts Institute of Technology, and he obtained his doctorate in 2020. He did research in Pablo Jarillo-Herrero's group studying graphene. After graduating, he has conducted postdoctoral research at MIT. See also * Bilayer graphene Bilayer graphene is a material consisting of two layers of graphene. One of the first reports of bilaye ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pablo Jarillo-Herrero
Pablo Jarillo-Herrero (born June 11, 1976, in Valencia) is a Spanish physicist and current Cecil and Ida Green Professor of Physics at Massachusetts Institute of Technology (MIT). Biography Jarillo-Herrero received in 1999 his Licenciatura in physics from the University of Valencia in Spain. Then he was two years at the University of California, San Diego, where he received a MSc in 2001. In 2005 at the Delft University of Technology in The Netherlands he earned his PhD, and continued on to a postdoc. In 2006 he moved to Columbia University, where he worked as a ''NanoResearch Initiative Fellow''. In January 2008 he joined MIT as an assistant professor of physics and received tenure. In 2018 he was promoted to Full Professor of Physics. In 2018 Jarillo-Herrero presented a new 2D-platform to investigate strongly correlated physics, based on graphene moiré superlattices. When Twistronics, two graphene sheets are twisted by an angle close to a ''magic angle'' theoretically p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superconductivity
Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Unlike an ordinary metallic conductor, whose resistance decreases gradually as its temperature is lowered even down to near absolute zero, a superconductor has a characteristic critical temperature below which the resistance drops abruptly to zero. An electric current through a loop of superconducting wire can persist indefinitely with no power source. The superconductivity phenomenon was discovered in 1911 by Dutch physicist Heike Kamerlingh Onnes. Like ferromagnetism and atomic spectral lines, superconductivity is a phenomenon which can only be explained by quantum mechanics. It is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor during its transitions into t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Two-dimensional Materials
In materials science, the term single-layer materials or 2D materials refers to crystalline solids consisting of a single layer of atoms. These materials are promising for some applications but remain the focus of research. Single-layer materials derived from single elements generally carry the -ene suffix in their names, e.g. graphene. Single-layer materials that are compounds of two or more elements have -ane or -ide suffixes. 2D materials can generally be categorized as either 2D allotropes of various elements or as compounds (consisting of two or more covalently bonding elements). It is predicted that there are hundreds of stable single-layer materials. The atomic structure and calculated basic properties of these and many other potentially synthesisable single-layer materials, can be found in computational databases. 2D materials can be produced using mainly two approaches: top-down exfoliation and bottom-up synthesis. The exfoliation methods include sonication, mechanical, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bilayer Graphene
Bilayer graphene is a material consisting of two layers of graphene. One of the first reports of bilayer graphene was in the seminal 2004 '' Science (journal), Science'' paper by Geim and colleagues, in which they described devices "which contained just one, two, or three atomic layers" Structure Bilayer graphene can exist in the AB, or Bernal-stacked form, where half of the atoms lie directly over the center of a hexagon in the lower graphene sheet, and half of the atoms lie over an atom, or, less commonly, in the AA form, in which the layers are exactly aligned. In Bernal stacked graphene, twin boundaries are common; transitioning from AB to BA stacking. Twisted layers, where one layer is rotated relative to the other, have also been extensively studied. Quantum Monte Carlo methods have been used to calculate the binding energies of AA- and AB-stacked bilayer graphene, which are 11.5(9) and 17.7(9) meV per atom, respectively. This is consistent with the observation that the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superconductive
Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Unlike an ordinary metallic conductor, whose resistance decreases gradually as its temperature is lowered even down to near absolute zero, a superconductor has a characteristic critical temperature below which the resistance drops abruptly to zero. An electric current through a loop of superconducting wire can persist indefinitely with no power source. The superconductivity phenomenon was discovered in 1911 by Dutch physicist Heike Kamerlingh Onnes. Like ferromagnetism and atomic spectral lines, superconductivity is a phenomenon which can only be explained by quantum mechanics. It is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor during its transitions into the s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boron Nitride Nanosheet
Boron nitride nanosheet is a two-dimensional crystalline form of the hexagonal boron nitride (h-BN), which has a thickness of one to few atomic layers. It is similar in geometry as well as physical and thermal properties to its all-carbon analog graphene, but has very different chemical and electronic properties – contrary to the black and highly conducting graphene, BN nanosheets are Insulator (electricity), electrical insulators with a band gap of ~5.9 eV, and therefore appear white in color. Uniform monoatomic BN nanosheets can be deposited by catalytic decomposition of borazine at a temperature ~1100 °C in a chemical vapor deposition setup, over substrate areas up to about 10 cm2. Owing to their hexagonal atomic structure, small lattice mismatch with graphene (~2%), and high uniformity they are used as substrates for graphene-based devices. Structure BN nanosheets consist of sp2-conjugated boron and nitrogen atoms that form a honeycomb structure. They contain ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Science (journal)
''Science'', also widely referred to as ''Science Magazine'', is the peer-reviewed academic journal of the American Association for the Advancement of Science (AAAS) and one of the world's top academic journals. It was first published in 1880, is currently circulated weekly and has a subscriber base of around 130,000. Because institutional subscriptions and online access serve a larger audience, its estimated readership is over 400,000 people. ''Science'' is based in Washington, D.C., United States, with a second office in Cambridge, UK. Contents The major focus of the journal is publishing important original scientific research and research reviews, but ''Science'' also publishes science-related news, opinions on science policy and other matters of interest to scientists and others who are concerned with the wide implications of science and technology. Unlike most scientific journals, which focus on a specific field, ''Science'' and its rival ''Nature'' cover the full r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Van Der Waals Force
In molecular physics, the van der Waals force is a distance-dependent interaction between atoms or molecules. Unlike ionic or covalent bonds, these attractions do not result from a chemical electronic bond; they are comparatively weak and therefore more susceptible to disturbance. The van der Waals force quickly vanishes at longer distances between interacting molecules. Named after Dutch physicist Johannes Diderik van der Waals, the van der Waals force plays a fundamental role in fields as diverse as supramolecular chemistry, structural biology, polymer science, nanotechnology, surface science, and condensed matter physics. It also underlies many properties of organic compounds In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The s ... and molecular solids, including their solubil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moiré Pattern
In mathematics, physics, and art, moiré patterns ( , , ) or moiré fringes are large-scale interference patterns that can be produced when an opaque ruled pattern with transparent gaps is overlaid on another similar pattern. For the moiré interference pattern to appear, the two patterns must not be completely identical, but rather displaced, rotated, or have slightly different pitch. Moiré patterns appear in many situations. In printing, the printed pattern of dots can interfere with the image. In television and digital photography, a pattern on an object being photographed can interfere with the shape of the light sensors to generate unwanted artifacts. They are also sometimes created deliberately – in micrometers they are used to amplify the effects of very small movements. In physics, its manifestation is wave interference such as that seen in the double-slit experiment and the beat phenomenon in acoustics. Etymology The term originates from '' moire'' (''moir� ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbital Magnetization
In quantum mechanics, orbital magnetization, Morb, refers to the magnetization induced by orbital motion of charged particles, usually electrons in solids. The term "orbital" distinguishes it from the contribution of spin degrees of freedom, Mspin, to the total magnetization. A nonzero orbital magnetization requires broken time-reversal symmetry, which can occur spontaneously in ferromagnetic and ferrimagnetic materials, or can be induced in a non- magnetic material by an applied magnetic field. Definitions The orbital magnetic moment of a finite system, such as a molecule, is given classically by : \mathbf_ = \frac\int d^3\mathbf \, \mathbf\times\mathbf(\mathbf) where J(r) is the current density at point r. (Here SI units are used; in Gaussian units, the prefactor would be 1/2''c'' instead, where ''c'' is the speed of light.) In a quantum-mechanical context, this can also be written as : \mathbf_ = \frac \langle\Psi \vert\mathbf \vert\Psi\rangle where −''e'' and ''me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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