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In physics, the moir茅 pattern is a specific geometrical design in which sets of straight or curved lines are superposed on top of each other. Recent studies have found that bilayers of transition metal dichalcogenide materials arranged in moir茅 patterns could be particularly promising for studying electronic phenomena and excitons (i.e., concentrations of energy in crystals formed by an excited electron and an associated hole).

Transition metal dichalcogenide moir茅 bilayers have advantageous characteristics for studying both electronic and excitonic physical phenomena, including strong Coulomb interactions. Past research studies have successfully used these systems to make several interesting discoveries, such as exotic charge orders at both integer and fractional fillings.

Researchers at University of Washington and other institutes worldwide have recently carried out a study specifically examining a Transition metal dichalcogenide moir茅 system comprised of molybdenum diselenide (MoSe₂)/tungsten diselenide (WSe₂) heterobilayers, Their paper, published in Nature 萌妹社区, reports the observation of moir茅-arranged trions (i.e., localized excitations consisting of three charged particles) in H-stacked MoSe₂/WSe₂ heterobilayers.

"Periodic moir茅 potential naturally occurs in transitional metal dichalcogenides moir茅 superlattices. Several years ago, that the periodic potential can function as arrays of quantum dots," Wang Yao, one of the researchers who carried out the study, told TechXplore. "Based on this idea, charge neutral moir茅 excitons in twisted MoSe₂/WSe₂ heterobilayers in 2019."

The work builds on the group's previous studies focusing on transitional metal dichalcogenides moir茅 superlattices. While in their past research, the team was able to observe charge-neutral moir茅 excitons in twisted MoSe₂/WSe₂ heterobilayers, in their new study, they tried to add the electrostatic control of the carrier density to the same moir茅 system. This ultimately enabled them to realize charged moir茅 excitons, which are also known as moir茅 trions.

"In our experiments, we measured the light emission from the heterolayers we examined," Xu explained. "By focusing on emission properties (linewidth, polarization, intensity, energy etc) as a function of carrier doping, magnetic field and temperature, we were able to identify moir茅 trions."

The findings could have important implications for the future development of new nanotechnology, as well as for the study of excitonic phenomena. In their future work, the team hopes to utilize moir茅 systems to investigate different physical phenomena.

"We showed that moir茅 potential can also trap charged excitons," Xu said. "Combined with the charge neutral ones, the heterobilayer can be used as a platform for studying both bosonic and fermionic many-body effects based on moir茅 excitons. In our next studies, we plan to study both equilibrium and non-equilibrium many body effects based on the moir茅 systems."

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