Category archives: Theoretical physics

The revolutionary theory of topological quantum chemistry , a description of the universal global properties of all possible band structures and materials, diagnoses topological phases based on elementary band representations. A set of bands is topological if it lacks an “atomic limit” that obeys the crystal symmetry (and time reversal, if desired): formally, an atomic […]

Chemists have a range of different spectroscopic techniques to study organic molecules. All of these techniques are based on spectra generated by a range of electronic transitions and vibrations, key excitations in matter, the study of which provides information about characteristics of materials and, therefore, allow their identification. In this context, one of those spectroscopic […]

The properties of bismuth have long defied classification, placing it in a category of its own. Now, as if it was not enough, it turns out its electronic structure has higher-order topology. This has been shown by an international team with the participation of Maia G. Vergniory (DIPC, Ikerbasque, UPV/EHU) and coordinated by Titus Neupert […]

Most of the theories describing dynamical processes at surfaces rely on the validity of the adiabatic Born-Oppenheimer approximation. What does this mean? We have already seen that adsorption commonly is understood as the reversible binding of molecules and atoms from the gaseous or liquid phase on surfaces, mostly of highly porous adsorbent media. In chemisorption […]

The progress that physics experienced during the 20 th century was probably one of the greatest and most everlasting successes of the humankind. Discovering the hidden and minute composition of matter and energy, as well as realising that the rules they obey are as further from common sense as quantum theory has revealed, are amongst […]

The wave nature of light expresses itself in the propagation all over space, showing an intrinsic limitation to be localized beyond the so-called diffraction limit which is of the order of half the wavelength of the photons propagating. However when interacting with matter, light often gets reflected, diffracted, scattered or absorbed depending on the interactions […]

The concept of moduli space is of utmost relevance in theoretical physics and mathematics, especially in geometry, topology and string theory. A moduli space is, roughly speaking, a space that classifies a given class of objects modulo an equivalence relation # which identifies the objects in that we want to consider as equivalent or, more […]

The electronic wave function of an n-electron molecule depends on 3n spatial and n spin coordinates. In a sense, the wave function of a many-electron molecule contains more information than is needed and is lacking in direct physical significance. This has prompted the search for methods that involve fewer variables than the wave function and […]

Topological insulators are materials with 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. Concretely, topological insulators are electronic materials that have a bulk band gap like an ordinary insulator but have […]

You may have read somewhere that atoms are actually made up mostly of empty space. The usual description goes more or less as follows. At the centre of each atom there is a very tiny nucleus, which carries all of the positive charge and nearly all of the mass of the atom. Surrounding the nucleus […]