Indirect Excitons

Non-technical Abstract: This work focuses on experimental studies of fundamental optical and electronic properties of structures made of thin layers of semiconductors. A special design of the structures on a length scale of a billionth part of a meter allows the creation of new quasi-particles called indirect excitons. The indirect excitons are unique because they can be cooled down to ultralow temperatures. Furthermore, the indirect excitons are unique because they have long lifetimes and can travel over long distances. In particular, the project address excitonic Bose polarons, which are recently found new quasiparticles in Bose gases of indirect excitons. This research increases our understanding of the physics of electronic systems in semiconductors. The students involved with this project have the opportunity to perform exploratory research on the cutting edge of contemporary physics. The potential impact of the project is in development of knowledge in condensed matter physics and increase of fundamental understanding of the optical and electronic properties of materials. Technical Abstract: This individual investigator award supports a project directed towards experimental studies of indirect excitons, also known as interlayer excitons, formed by electrons and holes in separated layers in a semiconductor heterostructure. Due to their long lifetimes, indirect excitons can cool below the temperature of quantum degeneracy. This gives an opportunity to study quantum systems of excitons. Indirect excitons can mediate spin transport. This gives an opportunity to study spin transport. The goals of the research are to study spin transport mediated by indirect excitons and to study excitonic Bose polarons – quasi-particles formed by direct excitons immersed in Bose gases of indirect excitons. The methods and approaches: Indirect excitons are formed either in GaAs heterostructures, which form a low-disorder platform for indirect excitons, or in van der Waals heterostructures composed of atomically thin layers of transition metal dichalcogenides, which form a platform where binding energies of indirect excitons are high. The studies include optical measurements of excitonic Bose polarons and spin transport mediated by indirect excitons. The research is performed by students, and it is integrated with education. The potential impact of the project is in development of knowledge in condensed matter physics and increase of fundamental understanding of optical and electronic properties of materials. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.