Superconductivity is a physical phenomenon in which some materials exhibit zero electrical resistance when cooled down below a certain critical temperature. As surprising as it can be, the critical temperature of these materials can be modified by reducing the sample size to about a million times the size of the objects we are used to […]
One of the greatest inventions of the 20th century, if not the greatest, was the transistor. It revolutionized the electronics industry and changed the way people around the world lived, learned, worked, and played. Its invention marked the beginning of solid state electronics which quickly reduced the size and power requirements of existing electronic tube […]
Chemistry • Condensed matter • Materials • Nanotechnology • Quantum physics
Usually, optical activity is understood as the ability some substances have to change the handedness of polarized light when it goes through them. Molecules that show optical activity have no plane of symmetry. The commonest case of this is in organic compounds in which a carbon atom is linked to four different groups. An atom […]
There are chemical compounds, called isomers, that have the same molecular formulae but different molecular structures or different arrangements of atoms in space. In constitutional isomerism the molecules have different molecular structures: i.e., they may be different types of compound, or they may simply differ in the position of the functional group in the molecule […]
Condensed matter • Materials • Nanotechnology • Quantum physics • Theoretical physics
Plasmonic nanostructures confine light to dimensions far smaller than the free-space wavelength, as they mix optical fields with electronic excitations. It was not until the 1990s, with the appearance of accurate and reliable nanofabrication techniques, that plasmonics blossomed. It was found then that local fields around nanostructures could be directly measured by near-field scanning optical […]
Symmetry is a unifying principle that governs all aspects of physics. The physical properties of crystalline solids are no different. But, as symmetry is progressively lowered through the 32 crystallographic point groups, novel transport effects emerge. Crystal symmetry dictates also the geometry of a phenomenon that has attracted a lot of attention in recent years […]
Condensed matter • Materials • Nanotechnology • Quantum physics
Nonlinear processes are attractive in microscopy and spectroscopy since they can be excited with light in the near‐infrared, which offers several advantages, from a deep tissue penetration capability or a reduced photodamage due to the lower photon energy, to a spatially more confined probed volume, which can result in an improved lateral resolution. These processes […]
Scanning tunneling microscopy (STM) is a technique in which a fine conducting probe is held close to the surface of a sample. Electrons tunnel between the sample and the probe, producing an electrical signal. The probe is slowly moved across the surface and raised and lowered so as to keep the signal constant. The precision […]
The concept of mean free path is very simple and straightforward: the average distance travelled between collisions by the molecules in a gas, the electrons in a metallic crystal, the neutrons in a moderator, etc. Assuming a couple of things about, for example, how elastic collisions are, it is not difficult to arrive to formulas […]
Condensed matter • Materials • Nanotechnology • Quantum physics
The so-called van der Waals materials consist of two-dimensional layers bound by weak van der Waals forces. After the isolation of graphene, the field of two-dimensional van der Waals materials has experienced an explosive growth and new families of two-dimensional systems and block-layered bulk materials have been created. This growth has been fueled mainly by […]