A silicate is any of a group of substances containing negative ions composed of silicon and oxygen. With this definition it is no surprise that silicates are a huge group. Natural silicates form the mayor component of most rocks, the bulk (90 %) of the Earth´s outer crust and one third of all minerals. The […]
The standard explanation of superconductivity goes more or less like this. Electrical resistance is due to collisions of the electrons (whether treated as particles or waves) with impurities, imperfections, and especially the lattice vibrations of the metal crystal. The lattice vibrations of the solid will decrease as the temperature falls, because the entropy, which represents […]
The absence of mirror symmetry, or chirality, is behind striking natural phenomena found in systems as diverse as DNA and crystalline solids. A remarkable example occurs when chiral semimetals with topologically protected band degeneracies are illuminated with circularly polarized light. In circularly polarized light, the tip of the electric vector describes a circular helix about […]
Transition metal dichalcogenides (TMDs) are layered compounds which can be thinned down to the single-layer limit. While mechanical exfoliation generates atomically thin TMD flakes possessing an area of a few square microns, chemical and physical methods provide high-quality monolayers on large-area substrates, which are suitable for actual technological applications. Similar to other two-dimensional materials, TMD […]
When you first study electromagnetism, all the electromagnetic waves you find are plane ones, waves in which the electric and magnetic fields are both orthogonal to the direction of travel of the wave. But this is a mode – the field pattern of the propagating wave – that is somehow ideal, as it exists in […]
Acenes are the class of organic compounds made up of linearly fused benzene rings. The best known of acenes is the compound with three rings, anthracene. The larger representatives, like pentacene (the one with five rings) have potential interest in optoelectronic applications and are actively researched in chemistry and electrical engineering. Starphenes are 2D polyaromatic […]
Isolated atomic planes, two-dimensional (2D) materials, like graphene can be reassembled into designer heterostructures made layer by layer in a precisely chosen sequence. Such heterostructures are often referred to as ‘van der Waals’ and the simpler one is composed of just two layers (bilayer). In 2018, Pablo Jarillo-Herrero, an experimentalist at MIT, found that at […]
Molecules when excited from their ground state (S 0 ) to their lowest electronically excited states often change their electronic structure considerably, which impacts on a range of important molecular properties. For example, the reactivity of a molecule in its excited state often differs markedly from that in its S 0 state. Also, the charge […]
A cement is any of various substances used for bonding or setting to a hard material. A popular one, Portland cement, is a mixture of calcium silicates and aluminates made by heating limestone (CaCO3) with clay (that contains aluminosilicates) in a kiln. The product is then ground to a fine powder. When Portland cement is […]
Back in 1929, theoretical physicist Hermann Weyl predicted the existence of a new elementary particle with intriguing properties. Specifically, it would be massless (like a photon), have half-integer spin (like an electron) and exist in two mirror-image versions (like left- and right-handed gloves)—a property known as chirality. Imagine there exist a material in which an […]