A quantum dot is a nanometric crystalline structure of semiconductor materials. In a quatum dot electrons are confined in a region of space, thus creating a well defined structure of energy levels that depends very much on the size and shape of the quantum dot. This structure resembles that of atoms, that is why sometimes […]
The ability to trap and control particles with the help of well-controlled electromagnetic fields has led to revolutionary advances in the fields of biology, condensed- matter physics, high-precision spectroscopy, and quantum information, enabling unprecedented control both in the study of isolated single particles as well as in few and many-body systems subject to controlled and […]
A dielectric is a nonconductor of electric charge in which an applied electric field causes a displacement of charge but not a flow of charge. Light propagation through a dielectric medium is determined by the spatial distribution of the material. Photons scatter at local variations of the refractive index. Therefore, how ordered the medium is […]
When light encounters molecules, the predominant mode of scattering is elastic scattering (Rayleigh). This scattering is responsible for the blue colour of the sky, for example. It is also possible for the incident photons to interact with the molecules in such a way that energy is either gained or lost so that the scattered photons […]
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, the so-called topological surface […]
There is a variable that is relevant for such seemingly different fields as outer space exploration , nanotechnology , fusion research , or medicine. And that is electronic stopping, its precise knowledge important for the understanding of space weathering, ion beam patterning, plasma-wall interactions, or radiation therapy, respectively. When ions propagate in matter, they are […]
According to how the electronic band theory is usually explained, solids can be classified as insulators, semiconductors, or metals. But, actually, there is another kind of solid between semiconductors and metals, the semimetals. In insulators and semiconductors the filled valence band is separated from an empty conduction band by a band gap, in metals there […]
In 1882, Heinrich Hertz devoted himself to the study of electromagnetism, including the recent and still generally unappreciated work of Maxwell. Two years later he began his famous series of experiments with electromagnetic waves. During the course of this work, Hertz discovered the photoelectric effect, which has had a profound influence on modern physics. The […]
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 […]