First-Principles Design of Charged Defects for Two-dimensional Quantum Technologies

University Of California-Santa Cruz, Santa Cruz CA

Investigators

Abstract

NONTECHNICAL SUMMARY This award supports research and education to develop computational methodologies aimed to investigate properties of defects, a kind of imperfection in solid materials. The PI will focus on defects in extremely thin materials, so thin that they are called 2D materials, and layered materials made from stacking them. Computational methods based on advanced theories can be used to help design defects in these materials so that they can be used to emit a single-quantum of light or photon. These single photon emitters can be the heart of building blocks for a new generation of information technology devices. Two-dimensional materials have major advantages over more traditional bulk materials, allowing, for example, easier production and integration into solid-state devices. Computational methods play a key role in designing 2D materials with defects for advanced sensing, computing, information, modeling and communications technologies. This project is aligned with NSF's Quantum Leap Big Idea. This project includes educational activities aimed to increase participation and representation of women in science, technology, engineering, and math (STEM) disciplines, especially in the physical sciences. Efforts in this project are planned to fill a significant gap in the physical and materials chemistry educational curriculum at University of California, Santa Cruz and build up theoretical/computational materials research on the campus under the umbrella of the Materials Science & Engineering Initiative. The activities include developing new computational materials courses for upper-division undergraduate and graduate students, providing undergraduate research opportunities through various existing programs and organizing workshops and seminars that offer career planning advices, especially for women students. TECHNICAL SUMMARY This award supports theoretical and computational research to develop computational methods and to investigate materials with potential application to quantum information technology. Defects in two-dimensional (2D) materials, such as ultrathin hexagonal Boron Nitride, have been found to be promising single-photon emitters with polarized and ultrabright single-photon emission at room temperature. This discovery opens new possibilities for emerging applications in nanophotonics and quantum information, with potentially much better scalability than the long-studied nitrogen vacancy center (NV-) in diamond. Despite the promising properties that have been experimentally demonstrated to date, accurate first-principles prediction of defect properties in 2D materials remains challenging. Difficulties arise mainly because of the highly anisotropic dielectric screening in 2D materials and the presence of strong many-body interactions, including electron-hole, electron-phonon, and defect-exciton interactions, which are not included in standard density functional theory computer codes. The plans to develop efficient computational methods to accurately determine defect charge transition levels and excited state lifetimes of defects in ultrathin 2D materials and heterojunctions, and then to use them to design complex defects with ideal properties for quantum emitters and quantum computation applications based on first-principles calculations. This research can contribute to resolving long-standing issues of simulating charged defects in 2D materials from first-principles, which necessitates proper treatment of electrostatic potentials of charges near a 2D plane and of the screened Coulomb interaction in many-body perturbation theory. Accurate electronic structure methods developed through this project can be used for determining defect charge transition levels, radiative exciton recombination lifetimes, and phonon-assisted non-radiative lifetimes in defective 2D monolayer and heterojunctions. They will also enable the rational design of quantum defects in 2D materials. This project includes educational activities aimed to increase participation and representation of women in STEM disciplines, especially in the physical sciences. Efforts in this project will fill a significant gap in the physical and materials chemistry educational curriculum at University of California, Santa Cruz (UCSC) and build up theoretical and computational materials research on the campus. Students from physics, chemistry, and engineering departments can join in the research and gain first-hand experience in computational materials research in the PI's group. The PI aims to recruit women and minority students to participate in these experiences. This project will also strengthen the research infrastructure at UCSC, a Hispanic Serving Institution. 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.