The question of the arrow of time has been on the table for centuries. The microscopic laws that determine the behaviour of matter (both in the classical and quantum regimes) are reversible. By seeing a video of a billiard board, with just a few balls, you will not be able to determine if the video […]
The discovery of superconductivity in 2D films dates back over 80 years. Initially, these were 2D metallic films deposited on inert substrates, but in recent times more exotic 2D systems have exhibited superconducting properties, such as the surface of topological insulators or twisted bilayer graphene. Superconductivity is caused by the interactions between atomic vibrations (phonons) […]
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. Part of this resistance appears at the surface, where electrons first encounter the material; as with electromagnetic radiation – […]
The magnitude of many of the exotic phenomena predicted for topological semimetals is directly proportional to something called the Chern number. Given the importance of the Chern number magnitude for these phenomena, it is just natural to wonder whether there is an upper limit for it and whether there are real materials in which this […]
No matter what you build or how much care you take building it, it would have defects. It seems it is a rule of nature: every time chaos gives way to order, from matter itself coming into existance in the very early universe to the formation of a crystal in a modern laboratory, defects appear […]
In science we try to be very precise with the wording of our texts. One of the consequences of this is that we are not afraid of repeating some words in a paragraph, or even in a sentence, if that contributes to avoid possible misunderstandings, even though it may be not recommended stylistically. Another feature […]
The concept of vector should be familiar: a quantity for which both magnitude and direction must be stated. This compares with a scalar quantity, where direction is not applicable, like temperature in a precise point. But, what if the magnitude varies with the direction? A vector would be a particular case, with only one direction […]
One of the most mysterious features of quantum mechanics is that if two particles (or photons) interact at some point in time then the properties of these particles will remain connected at future times. A consequence of this is that determining the quantum state of one of the particles simultaneously determines the quantum state of […]
Graphene is a diamagnetic material, this is, unable of becoming magnetic. However, a triangular piece of graphene is predicted to be magnetic. This apparent contradiction is a consequence of “magic” shapes in the structure of graphene flakes, which force electrons to “spin” more easily in one direction. Triangulene is a triangular graphene flake, which possesses […]
Condensed matter • Materials • Nanotechnology • Quantum physics • Theoretical physics
When two photons with the same energy interact with a nonlinear material, they “combine” and generate a new photon with twice the energy of the initial photons. More precisely, two photons at the fundamental frequency are absorbed by a plasmonic structure to emit one photon at the second-harmonic frequency. This is called second-harmonic generation. Second-harmonic […]