Using light to put a twist on electrons
Some molecules, including most of the ones in living organisms, have shapes that can exist in two different mirror-image versions. The right- and left-handed versions can sometimes have different properties, such that only one of them carries out the molecule’s functions. Now, a team of physicists has found that a similarly asymmetrical pattern can be induced and measured at will in certain exotic materials, using a special kind of light beam to stimulate the material. In this case, the phenomenon of “handedness,” known as chirality, occurs not in the structure of the molecules themselves, but in a kind of patterning in the density of electrons within the material. The researchers found that this asymmetric patterning can be induced by shining a circularly polarized mid-infrared light at an unusual material, a form of transition-metal dichalcogenide semimetal called TiSe2, or titanium diselenide. The new findings, which could open up new areas of research in...