This CAREER award supports theoretical research that explores the phases, collective excitations, and transport and photoluminescence signatures of excitonic condensates in double-layer graphene and related systems. Using momentum-space mean-field analysis, the complementary real-space tight-binding method, and the effective action approach, the PI will focus on the following open questions:
1) What are the transport and photoluminescence properties of uniform and crystalline excitonic condensates?
2) How do electronic screening, magnetic field, and the surface curvature affect them?
3) What are the signatures of BEC-BCS crossover in (non-uniform) condensates?
4) What are the differences between the results for a double-layer graphene system and other two-dimensional systems?
The educational and outreach component of the proposal involves the training and mentoring of a postdoctoral fellow, a graduate student, as well as undergraduate and high school students. The PI will involve high school and undergraduate students in research and scholarly activities that emphasize the duality between textbook learning and research. The research will be translated into self-contained pedagogical modules that can be incorporated into the undergraduate curriculum. The hands-on research experience for K-12 students will be complemented with periodic dissemination of exciting discoveries in science through a website and school-visits.
NON-TECHNICAL SUMMARY
This CAREER award supports theoretical research that explores the possibilities and various properties of "excitonic condensates" in a relatively new class of materials. When light interacts with semiconductors or insulators and excites an electron from an occupied quantum state to an unoccupied one leaving behind an effective positive charge called the "hole", the electrostatic interaction between the negatively charged electron and the positively charged hole results in the formation of a bound state of these two entities called the "exciton". Due to quantum mechanical laws, it is possible for excitons to condense into the same lowest-energy state or form a liquid-like state in which they can flow without any viscosity, thereby forming "excitonic condensates". While such condensates are technologically important because they make zero-resistance electronic transport and coherent sources of light possible, progress towards their realization has been has been hampered due to materials whose properties are not widely tunable. Recently, a two-dimensional honeycomb network of carbon atoms, called graphene, has emerged as an exceptionally versatile, clean, and tunable electronic material. It is believed that graphene is a promising candidate for the realization of excitonic condensates.
The PI will investigate the possibilities of excitonic condensation in a system of two layers of graphene stacked on top of another under various circumstances, and predict their signatures in electrical transport and light-emission measurements. The research will also address fundamental questions about excitonic condensates, and the results are expected to be applicable to a wide variety of systems.
The educational and outreach component of the proposal involves the training and mentoring of a postdoctoral fellow, a graduate student, as well as undergraduate and high school students. The PI will involve high school and undergraduate students in research and scholarly activities that emphasize the duality between textbook learning and research. The research will be translated into self-contained pedagogical modules that can be incorporated into the undergraduate curriculum. The hands-on research experience for K-12 students will be complemented with periodic dissemination of exciting discoveries in science through a website and school-visits.
