The current in a semiconductor consists of two parts: the negatively charged electrons in the conduction band and the positively charged holes in the valence band. Although the number of electrons in the conduction band is equal to the number of holes in the valence band, the two contributions to the current are in general […]
In nanophysics one is dealing with physical systems that are formed of parts consisting of a relatively small number of atoms; these systems are typically less than 100 nm in size. As a consequence quantum and surface effects are extremely important. The subject can be traced back to a remarkably visionary and famous talk given […]
Computer science • Condensed matter • Materials • Physics • Quantum physics
When quantum computing comes, it very likely will rely for the fast storage and processing of information on spintronics. Spintronics (from spin transport electronics) is a branch of technology that specifically makes use of quantum-mechanical spin, and especially of the transport of that spin, in electronic devices. Spin is the part of the total angular […]
It is likely that you have read somewhere that gravity is much weaker than the electromagnetic interaction. And it is true: for the electron and the proton gravity is 39 orders of magnitude weaker. Still what governs the movement of moons, planets, stars and galaxies is gravity; even the existence of dark matter is deduced […]
No matter how the layout of the periodic table may be, there are elements that are always grouped together. This is easy to understand; let’s take for example the standard form of the table (due to H.G. Deming). In this layout each group, each vertical column in the table, has more significant periodic trends than […]
Graphene is a material with outstanding electronic characteristics. Many of them arise from the cone-like dispersion of charge carriers near the Fermi level (at which the occupation probability of energy levels is 0.5), where electrons behave as relativistic Dirac fermions, i.e., as if they had no mass. This excellent video from toutestquantique.fr summarizes them very […]
The exotic properties of layered materials have become a major focus of scientific research. The most famous member of this group is graphene which serves as a building block for few layered graphene and graphite as well as for single- and multi-walled carbon nanotubes. Here, each layer is an one-atom thick hexagonal sheet of sp […]
In an electromagnetic wave, the direction of the electric field is perpendicular to the direction of propagation of the wave. We say the wave is circularly polarized if the tip of the vector that represents the electric field describes a circular helix (thus circular polarization is sometimes called helicity) about the direction of propagation. Waves […]
An electric current can be visualized as a flow of electrons through a conducting piece of material. The less the resistance the material structure opposes to the flow of electrons the better a conductor it is. A part of this resistance appears at the surface of the material, where the electrons first encounter it; as […]
One of the main features of a F1 car is aerodynamics. How the car minimizes the drag imposed by the fact it is moving through a fluid, air, and how it takes advantage of the forces this movement generates to keep it stuck to the track, are most important for its performance. Even though the […]