Exotic spiralling electrons discovered by physicists

Physicists have discovered an exotic form of spiralling electron — which spins like a planet — with profound implications for advances in lighting, lasers, solar cells and quantum computing.

Physicists from Rutgers and other institutions have discovered an exotic form of electron pairs which spiral like planets. The electrons pairs — known as ‘chiral-surface-excitons’ — consist of particles and anti-particles bound together and swirling around each other on the surface of solids, according to a study in the Proceedings of the National Academy of Sciences.

The two types of ‘chiral surface excitons’ are on the right and left side of the image. They are generated by right- and left-handed light (photons in blue). The excitons consist of an electron (light blue) orbiting a ‘hole’ (black) in the same orientation as the light. The electron and hole are annihilated in less than a trillionth of a second, emitting light (photons in green) that could be harnessed for lighting, solar cells, lasers and electronic displays (Hsiang-Hsi (Sean) Kung/Rutgers University-New Brunswick)

As lead author Hsiang-Hsi (Sean) Kung, a graduate student in Physics Professor Girsh Blumberg’s Rutgers Laser Spectroscopy Lab at Rutgers University-New Brunswick, explains: “Excitons are created by shining intense and energetic light on solids, which kick the negatively charged electrons out of their equilibrium position, leaving behind positively charge “holes”.

“The electrons and holes are like fast spinning tops that naturally bound with each other through the attractive electric force called Coulomb interaction.”

These electrons eventually “spiral” towards the holes, annihilating each other while emitting a kind of light called ‘photoluminescence’ within a trillionth of a second. By studying this light, physicists can understand the properties of electrons and the ‘holes’ they leave in the surface of a conductor. This phenomenon has applications for devices such as solar cells, lasers and TV and other displays.

Hsiang-Hsi (Sean) Kung, continues: “Excitons are old and well-known objects in semiconductors since the late 50s, their applications are in our everyday lives ranging from solar cells to lasers. However, excitons in semimetals and metals are not yet well understood.”

The scientists discovered chiral — meaning left or right ‘handed’ — excitons on the surface of a crystal known as bismuth selenide, which could be mass-produced and used in coatings and other materials in electronics at room temperature.

A sample of Bismuth selenide a material that could have profound implications for quantum computing

Senior author, Physics Professor Girsh Blumberg, explains: “Bismuth selenide is a fascinating compound that belongs to a family of quantum materials called ‘topological insulators’.

“They have several channels on the surface that are highly efficient in conducting electricity.”

The basic structural unit for bismuth selenide is a five-layer sandwich made up of alternating single-atom sheets of selenium (orange) and bismuth (purple).

Bismuth selenide has the potential to be an important material in the development of quantum computing.

Hsiang-Hsi (Sean) Kung, says: “Together with the semimetallic properties, we believe our study could expand the applications of bismuth selenide in optoelectronics — the combined use of light and electronics.”

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