When you look at a crystal—say, a piece of salt or a sheet of graphene—its atoms are not randomly scattered. They form an orderly grid, like tiles on a floor. Because the atoms are arranged in this repeating way, electrons moving through the crystal don’t behave as if they’re in free space. Instead, their motion […]
Superconductivity, the phenomenon where electrical current flows without resistance, has long captivated scientists and engineers. This unique state of matter holds promise for revolutionizing technologies, from power grids to magnetic levitation. A recent study delves into the intriguing world of graphene-based superconductors, shedding light on how twisting multiple layers of graphene can influence their superconducting […]
Twisted bilayer graphene (TBG) has garnered significant attention due to its unique electronic properties, especially when the two graphene layers are misaligned by a specific “magic” angle. This misalignment leads to the formation of moiré patterns, resulting in flat electronic bands that enhance electron interactions and give rise to phenomena such as superconductivity and insulating […]
Twisted bilayer and multilayer systems represent two-dimensional materials, where atom-thick layers of the same or different materials are superimposed and rotated by an arbitrary twist angle. Twisted bilayer graphene (TBG) represents arguably the most prominent physical system of this kind, the bilayers of transition metal dichalcogenides (TMD) the other. The effect of twisting two periodic […]
Some materials have special universal properties 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. So-called topological insulators are electronic materials that have a bulk band gap like an ordinary insulator but have conducting states on their […]
The band theory of metals has been experimentally tested many times and is now the accepted model of the behaviour of conductors and insulators. Electrical resistance is due to collisions of the electrons (whether treated as particles or waves) with impurities, imperfections, and especially the lattice vibrations of the metal crystal. The lattice vibrations of […]
Twisted bilayer graphene (TBG) has taken the spotlight in the condensed matter community since the discovery of correlated phases. Now, a team of researchers studies heterostructures of TBG and hexagonal boron nitride (hBN) using an atomistic tight-binding model together with semi-classical molecular dynamics to consider relaxation effects. Isolated atomic planes, two-dimensional (2D) materials, like graphene […]
Imagine a conductor or a semiconductor through which a current is flowing. Then we apply a strong transverse magnetic field. As a result, we can measure a potential difference at right angles to both the current and the field caused by the deflection of charge carriers by the field. This effect was described by Edwin […]
An exciton can be described as an electron-hole pair in a crystal that is bound in a manner analogous to the electron and proton in a hydrogen atom. Thus, the exciton behaves like an atomic excitation that passes from one atom to another. Exciton energy states involve a band with a particular dispersion law that […]
Twistology could be the study of unexpected changes or developments in stories or situations, from coups d’état to the fatherhood of Darth Vader. In condensed matter physics there is something similar, although the preferred name is twistronics (from twist and electronics). It is understood as the study of how the angle (the twist) between layers […]