Major technological revolutions have occurred when the humankind has been able to harness natural resources, such as fire, electricity or nuclear energy. We are now in the verge of the so called second quantum revolution, that aims to harness two of the weirdest natural resources, coherence and entanglement. This is a tall order that calls […]
Interfacial electron transfer constitutes the key step in the conversion of solar energy into electricity and fuels. Required for fast and efficient charge separation, strong donor−acceptor interaction is typically achieved through covalent chemical bonding…or not. Experiences with donor−acceptor molecular diads and triads, conjugated polymers, and DNA, leads to the expectation that a covalent bonding is […]
Extended and refined by Bloch and others during the 1930s, Bloch’s theory, known as the band theory of solids, accounts very well for the conducting behaviour of materials. When atoms are joined together into a crystal, each of the individual quantum states of the atoms joins with the corresponding states in other (identical) atoms in […]
Topological insulators are electronic materials that have a bulk band gap like an ordinary insulator but have conducting states on their edge or surface. The conducting surface is not what makes topological insulators unique, but the fact that it is protected due to the combination of spin-orbit interactions and time-reversal symmetry. Researchers are chasing efficient […]
For centuries, metals were employed in optical applications only as mirrors and gratings. New vistas opened up in the late 1970s and early 1980s with the discovery of surface-enhanced Raman scattering and the use of surface plasmon (collective electronic oscillations at the surface of metals) resonances for sensing. However, it was not until the 1990s […]
Over geologic time scales, seawater transforms the basalt of the ocean floor by chemical attack. At the end of this alteration process, the basalt turns partly into clays and partly into dissolved salts in sea water. Lithium, a chemical element initially contained in basalt, will then be distributed between clay and seawater. This separation has […]
The idea that certain natural products such as rubber are composed of giant molecules, or polymers, consisting of many repeating units linked by covalent bonds arose largely from the work of the German chemist Hermann Staudinger (1881–1965) in the early 1920s. He convinced skeptical chemists of this idea partly by linking small organic molecules (monomers) […]
There are compounds, called isomers, that have the same molecular formulae but different molecular structures or different arrangements of atoms in space. In the so-called cis-trans isomerism, isomers have different positions of groups or specific atoms with respect to a double bond, a ring or a central atom. For example, the numbers in the name […]
Condensed matter • Materials • Nanotechnology • Quantum physics • Theoretical physics
So-called “valleytronics” is a new type of electronics that could lead to faster and more efficient computer logic systems and data storage chips in next-generation devices. Valley electrons are so named because they carry a valley “degree of freedom.” This is a new way to harness electrons for information processing that’s in addition to utilizing […]
We have considered in some previous articles the importance of the spin-orbit interaction. But it is interesting to go through some basic concepts we have seen elsewhere once again in order to grasp the surprising discovery we will be talking about below. The analogy for the spin usually goes this way: Imagine that the electron […]