That was a first, but mysteries remained, especially in results obtained at low or zero magnetic fields. Kono said the team didn't understand at the time why the wavelength of the burst changed over its 100-picosecond span. Now they do. The team included co-lead authors Timothy Noe, a Rice postdoctoral researcher, and Ji-Hee Kim, a former Rice postdoctoral researcher and now a research professor at Sungkyunkwan University in the Republic of Korea.
In the new results, the researchers not only described the mechanism by which the light's wavelength evolves during the event (as a Fermi-edge singularity), but also managed to record it without having to travel to the National High Magnetic Field Laboratory at Florida State.
Kono said superfluorescence is a well-known many-body, or cooperative, phenomenon in atomic physics. Many-body theory gives physicists a way to understand how large numbers of interacting particles like molecules, atoms and electrons behave collectively. Superfluorescence is one example of how atoms under tight controls collaborate when triggered by an external source of energy. However, electrons and holes in semiconductors are charged particles, so they interact more strongly than atoms or molecules do.
The quantum well, as before, consisted of stacked blocks of an indium gallium arsenide compound separated by barriers of gallium arsenide. "It's a unique, solid-state environment where many-body effects completely dominate the dynamics of the system," Kono said.
"When a strong magnetic field is applied, electrons and holes are fully quantized that is, constrained in their range of motion -- just like electrons in atoms," he said. "So the essential physics in the presence of a high magnetic field is quite similar to that in atomic gases. But as we decrease and eventually eliminate the magnetic field, we're entering a regime atomic physics cannot access,
|Contact: David Ruth|