Indirect Excitons in Semiconductor Nanostructures

University Of California-San Diego, La Jolla CA

Investigators

Abstract

****NON-TECHNICAL ABSTRACT**** This individual investigator award supports experimental studies of fundamental optical and electronic properties of structures made of very thin layers of semiconductors. These nanoscale structures (i.e, they have a tiny length scale of a billionth of a meter) are designed to allow the creation of new entities called "indirect excitons". Modern signal processing devices, such as computers, are based on electronic control while optical communication plays a major role in signal transmission. Since both signal processing and transmission are required for practical electronic devices, finding an effective optoelectronic system, which unifies electronic operations and optical communications, could revolutionize electronics. Indirect excitons can be electronically controlled and can produce optical signals, therefore these entities may be important for future optoelectronic devices. Furthermore, indirect excitons are unique because they can be cooled to ultralow temperatures where they start to behave in a quantum mechanical fashion. This project seeks to increase our understanding of the fundamental physics of ultracold indirect excitons. In particular it will address the predicted quantum mechanical behavior of the indirect excitons. The potential impact of the project is in development of increased knowledge in condensed matter physics, in general, and more specifically an increased fundamental understanding of the optical and electronic phenomena observed in materials. Such understanding may lead to the exciting possibility of developing advanced optoelectronic devices. The students involved with this project will have the opportunity to perform exploratory research on the cutting edge of contemporary physics. ****TECHNICAL ABSTRACT**** This individual investigator award supports experimental studies of cold exciton gases in semiconductor nanostructures. An exciton is an electron-hole bound pair in a semiconductor. At low densities excitons are hydrogen-like, weakly interacting Bose particles. It has been predicted that the quantum degeneracy temperature of an exciton gas is relatively high, about 1K. Due to their long lifetime and high cooling rate, indirect excitons in coupled quantum wells form a system where a cold exciton gas can be created. Moreover, indirect excitons can be controlled optically and electronically. This project will explore the unique opportunities for implementation and control of quantum bosonic gases in semiconductor nanostructures. In particular, the project will investigate new states in quantum exciton gases, including theoretically predicted exciton condensates and a recently observed new state - the macroscopically ordered exciton state. This research is expected to increase our fundamental understanding of optical interactions and quantum coherence in many bodied systems. The proposed research will be performed by students and will be integrated with education.