Category archives: Quantum physics

Density functional theory (DFT) is a theoretical treatment of molecules in which the electron density is considered rather than the wave functions of individual electrons. In other words, it is a way of describing many-electron, in general, many-fermion, systems in which the energy is a funtional of the density of electrons (fermions). DFT is without […]

Topological materials have special universal properties, which are protected against perturbations. Such properties are theoretically described by topology, a branch of mathematics concerned with the properties of geometrical objects that are unchanged by continuous deformations. Topological materials behave like an ordinary insulator in the bulk but have conducting states on their boundaries, i.e., edges or […]

Symmetries play a fundamental role in Physics, and more specifically in Quantum Physics. It is well known that symmetries lead to degeneracy and to conserved currents in closed quantum systems (meaning that they do not interact with an environment). In the more realistic scenario of Open Quantum Systems (meaning that the quantum system does interact […]

The most famous conjecture in condensed-matter physics was proposed in 1935, when Hillard Huntington and Eugene Wigner calculated the properties of hydrogen squeezed to high density and pressure. They predicted that under pressures above 25 gigapascals (GPa), hydrogen would undergo a density-driven transition from an insulating, molecular solid to a conducting, atomic solid. In their […]

Light emission from emitters is a valuable piece of information in a variety of sensing and detection techniques, capable of labeling physical and biological processes which occur in the proximity of the emitter. Furthermore, quantum technologies are currently exploiting the statistics of single-emitters light emission aiming at turning particular emitters into fundamental units to sustain […]

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 […]