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. So-called chiral matter broadly describes structures for which left- or right-handed mirror images are non-superimposable, or, equivalently, that lack improper rotation axes […]
Spintronic devices are based on the inherent spin magnetic moment of the electron, the same way electronic ones are on just its charge, to store and process information. These devices should, in theory, operate faster and at lower temperatures than their current electronic-only counterparts because an electron’s spin can be flipped much quicker than its […]
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 […]
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 […]
Electron correlations and topology are well established as engines for surprising and potentially functional properties. Strong correlations promote quantum fluctuations, which engender abundant phases of matter and various quantum phase transitions. Meanwhile, extensive developments have taken place in noninteracting electron systems, especially those with sizable spin-orbit couplings. It can reasonably be expected that the intersection […]
Several classes of correlated electron systems such as cuprates, iron-pnictides, iron-chalcogenides, and several heavy-fermion compounds, have been identified as unconventional superconductors. More recently, superconductivity with unconventional features has also been identified in twisted bilayer graphene. In this vein, the electronic correlations intrinsically present in transition metal dichalcogenides (TMDs), a family of layered materials, are promising […]
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 […]
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, such as tetradymite-like topological insulators – electronic materials that have […]
The scattering of conduction electrons in metals due to impurities with magnetic moments is known as the Kondo effect, after Jun Kondo, who analysed the phenomenon in 1964. This scattering increases the electrical resistance and has as a consequence that, in contrast to ordinary metals, the resistance reaches a minimum as the temperature is lowered […]
Diodes are everywhere these days as they are key elements for electronics, optics, and detection. A diode is an electronic device with two electrodes. In the obsolescent thermionic diode a heated cathode emits electrons, which flow across the intervening vacuum to the anode when a positive potential is applied to it. The device permits flow […]