Study Sheds New Light on Quasiparticles and Their Interactions

Scientists have disclosed latest information regarding the mass of each component that constitutes a potential quasiparticle, called an exciton. The exciton could play a major role in better upcoming applications for memory storage, quantum computing, and more efficient conversion of energy.

The research team was headed by Sufei Shi, who works as an assistant professor of chemical and biological engineering at Rensselaer Polytechnic Institute.

The researchers’ study, recently published in the Nature Communications journal, brings investigators one step forward to progress the development of semiconductor devices by improving their interpretation of transitional metal dichalcogenides (TMDCs)—an atomically thin class of materials. TMDCs have attracted considerable attention for their optical and electronic characteristics.

Despite this fact, scientists still need to learn more about the exciton before they can effectively use the TMDCs in technological devices.

Shi and his research team have turned out to be frontrunners in that quest, analyzing and developing TMDCs, and particularly, the exciton. Excitons are usually produced by light energy and they form when a positively charged hole particle couples with a negatively charged electron.

The researchers from Rensselaer Polytechnic Institute discovered that within this atomically thin class of semiconductor material, the communication between holes and electrons can be so powerful that the pair of particles inside an exciton can form a trion by coupling with a third hole or electron particle.

In the latest study, Shi’s research team successfully exploited the TMDCs, causing the vibration of the crystalline lattice within. This produced another form of quasiparticle called a phonon, which will robustly communicate with a trion.

Then, the scientists positioned the material inside a high magnetic field, examined the light produced from the TMDCs from the phonon interaction, and successfully ascertained the effective mass of the hole and the electron separately.

Earlier it was believed that mass will have a symmetry but the Rensselaer researchers discovered that such measurements were considerably different, added Shi.

We have developed a lot of knowledge about TMDCs now. But in order to design an electronic or optoelectronic device, it is essential to know the effective mass of the electrons and holes. This work is one solid step toward that goal.

Sufei Shi, Assistant Professor, Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute

Zhipeng Li, a postdoctoral researcher at Rensselaer Polytechnic Institute, and Tianmeng Wang and Shengnan Miao—both doctoral students in chemical engineering at Rensselaer Polytechnic Institute—also headed the study.

In addition, the study was performed in association with a theoretical research team headed by Chuanwei Zhang, a professor of physics at the University of Texas based in Dallas, researchers from Maglab in Tallahassee, and also crystal growers from Japan and Arizona State University.

The research is mainly funded by a National Science Foundation CAREER award and an Air Force Office of Scientific Research grant.

Video Credit: Rensselaer Polytechnic Institute.

Journal Reference:

Li, Z., et al. (2020) Phonon-exciton interactions in WSe₂ under a quantizing magnetic field. Nature Communications. doi.org/10.1038/s41467-020-16934-x.