Exciting Patterns Found in Excitons

Guest_Jim_* - April 5, 2012 12:26PM in Science & Technology

Have you ever wondered what happens when an electron is excited out of its orbit in a semiconductor? The answer is nothing too complex; a positively charged hole is left behind. What is complex though, is what can happen between these two things.

Excitons are the quasiparticles made of an electron and the hole it produced. Like real quantum particles, excitons can have angular momentum, or spin, but they do not behave like other particles. When chilled to near absolute zero, excitons group together into droplets that resemble a pearl necklace. Researchers at the University of California, San Diego successfully cooled these ‘pearls’ to one tenth the previous record, which allowed them to then measure the spin of the excitons. What they found was rather unexpected as the excitons did not spin together within the droplets, but in a pattern that surround the droplet. The researchers have named these patterns spin textures and found the texture of a droplet is influenced by the spin polarization and phase singularities of the excitons.

These findings could influence potential optoelectronics, as excitons influence the optical properties of semiconductors, and could even lead to excitonic devices.