Semiconductors Exhibit 'Crowd-Like' Behavior

Researchers have used ultrafast lasers to reveal a collective, "crowd-like" electronic behavior in semiconductors. The work may help researchers better predict characteristics of optoelectronic devices like emission signal magnitude and phase, which are especially significant in optics. Currently, subtle interactions in the semiconductor that were not previously detected made optoelectronic design somewhat imprecise. Recent work at JILA—a joint venture of the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder—revealed these interactions using a highly-sensitive method of manipulating laser light energy and phase. The JILA team took a sample made of thin layers of gallium arsenide and hit it with a continuous series of three near-infrared laser pulses lasting just 100 femtoseconds each, according to an NIST release. Trillions of electronic structures called excitons—large particles consisting of excited electrons and the "holes" they left behind as they jumped to higher-energy vibration patterns—were formed. Researchers subsequently observed a subtle coupling between pairs of excitons with different energy levels. This "crowd-like" behavior of electronic particles can shift the phase of any deflected light, according to the release. The work, an adaptation of a previously-developed technique to probe correlations between spinning nuclei as an indicator of molecular structure, was published in the Proceedings of the National Academy of Sciences.