糖心视频

An international research team led by the University of G枚ttingen has, for the first time, observed the build-up of a physical phenomenon that plays a role in the conversion of sunlight into electrical energy in 2D materials. The scientists succeeded in making quasiparticles鈥攌nown as dark Moir茅 interlayer excitons鈥攙isible and explaining their formation using quantum mechanics. The researchers show how an experimental technique newly developed in G枚ttingen, femtosecond photoemission momentum microscopy, provides profound insights at a microscopic level, which will be relevant to the development of future technology. The results were published in Nature.

Atomically thin structures made of two-dimensional semiconductor materials are promising candidates for future components in electronics, optoelectronics and photovoltaics. Interestingly, the properties of these semiconductors can be controlled in an unusual way: like Lego bricks, the atomically thin layers can be stacked on top of each other.

However, there is another important trick: while Lego bricks can only be stacked on top鈥攚hether directly or twisted at an angle of 90 degrees鈥攖he angle of rotation in the structure of the semiconductors can be varied. It is precisely this angle of rotation that is interesting for the production of new types of solar cells. However, although changing this angle can reveal breakthroughs for new technologies, it also leads to experimental challenges.

In fact, typical experimental approaches have only indirect access to the moir茅 interlayer excitons, therefore, these excitons are commonly termed "dark" excitons. "With the help of femtosecond photoemission momentum microscopy, we actually managed to make these dark excitons visible," explains Dr. Marcel Reutzel, junior research group leader at the Faculty of 糖心视频ics at G枚ttingen University. "This allows us to measure how the excitons are formed at a time scale of a millionth of a millionth of a millisecond. We can describe the dynamics of the formation of these excitons using quantum mechanical theory developed by Professor Ermin Malic's research group at Marburg."

"These results not only give us a fundamental insight into the formation of dark Moir茅 interlayer excitons, but also open up a completely new perspective to enable scientists to study the optoelectronic properties of new and fascinating materials," says Professor Stefan Mathias, head of the study at G枚ttingen University's Faculty of 糖心视频ics. "This experiment is ground-breaking because, for the first time, we have detected the signature of the Moir茅 potential imprinted on the exciton, that is, the impact of the combined properties of the two twisted semiconductor layers. In the future, we will study this specific effect further to learn more about the properties of the resulting materials."

This research was published in Nature.