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The two types of "chiral surface excitons" are located to the right and left of the image. They are generated by the right and left light (photons in blue). The excitons consist of an electron (light blue) orbiting a "hole" (black) of the same orientation as light. The electron and the hole are annihilated in less than one trillion seconds and emit a light (photons in green) that could be exploited for illumination, solar cells, lasers and electronic displays . Credit: Hsiang-Hsi University (Sean) Kung / Rutgers – New Brunswick
Rutgers and other physicists have discovered an exotic form of electrons that spin like planets and could lead to advances in lighting, solar cells, lasers and electronic displays.
This is what is called a "chiral surface exciton", and it consists of particles and antiparticles bound and swirling on each other on the surface of solids, according to a study of the Proceedings of the National Academy of Sciences.
Chiral refers to entities, such as your right and left hands, that match but are asymmetrical and can not be superimposed on their mirror image.
Excitations form when the intense light shines on the solids, eliminating the negatively charged electrons and leaving behind "holes", according to lead author Hsiang-Hsi (Sean) Kung, a graduate student in physics from the lab. Rutgers laser spectroscopy of Professor Girsh Blumberg at Rutgers University-New Brunswick.
The electrons and holes look like vertices in rapid rotation. The electrons end up "spiraling" toward the holes, canceling in less than a trillion seconds while emitting a kind of light called "photoluminescence". This discovery has applications for devices such as solar cells, lasers and television screens and the like.
Scientists have discovered chiral excitons on the surface of a crystal called bismuth selenide, which could be mass-produced and used in coatings and other electronic materials at room temperature.
"Bismuth selenide is a fascinating compound that belongs to a family of quantum materials called" topological insulators, "said lead author Blumberg, a professor in the Department of Physics and Astronomy at the Faculty of Arts. and sciences. "They have several channels on the surface that are very effective for driving electricity."
The dynamics of chiral excitons is not yet clear and scientists want to use ultra-fast imaging to deepen them. Chiral surface excitons can also be found on other materials.
Explore further:
A sea of electrons in rotation: the discovery could generate a wave of new electronic devices
More information:
H.-H. Kung el al., "Observation of chiral surface excitons in a Bi2Se3 topological insulator," PNAS (2019). www.pnas.org/cgi/doi/10.1073/pnas.1813514116
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