Probing Ultrafast Carrier Spin Dynamics in Pb-free Metal Halide Double Perovskites

With the support of the Macromolecular, Supramolecular, and Nanochemistry (MSN) program in the Division of Chemistry, Professor Jin Zhang of University of California-Santa Cruz and Professor Yuan Ping of University of Wisconsin-Madison are using advanced computational and laser techniques to study the behavior of electron spin in two-dimensional (2D) metal halide double perovskites. Electron spin is a fundamental quantum mechanical property useful for applications such as information encoding and storage. Many emerging applications require long spin state lifetime and precise control. However, spin lifetime is usually short, a fraction of a second, and challenging to manipulate and use in devices. The research will create new 2D perovskites with long spin lifetimes and use ultrafast lasers to probe and control spin. Their discoveries could impact technologies from nanoelectronics to quantum information technologies including quantum computing and communication. The project will also provide training opportunities for future scientists, and through their “open lab” with a theme on “Spectroscopy and Sunny Santa Cruz” (SSSC)”, it will introduce research to local high school students and communities to enhance public awareness about science. With the support of the Macromolecular, Supramolecular, and Nanochemistry (MSN) program in the Division of Chemistry, Professor Jin Zhang of University of California-Santa Cruz and Professor Yuan Ping of University of Wisconsin-Madison are using combined advanced computational and experimental efforts to study spin and carrier relaxation in novel 2D lead-free metal halide double perovskites. This is motivated by the novel spin-orbit physics hosted in this class of material, which is highly tunable through crystal symmetry, morphology, and chemical composition in these systems. Meanwhile, electron-phonon and electron-electron scatterings lead to spin relaxation through spin-orbit coupling and lead to finite spin lifetime, which can be determined using ultrafast laser experiments with circularly polarized light. The project will systematically study the fundamental factors, such as structure, composition, surface, and chiral component, which affect the electron spin lifetime by studying the impact of each factor on spin lifetime as well as associated processes such as electron-electron, electron-surface, and electron-phonon scatterings. The materials will be synthesized with rational structural and compositional control, and carefully characterized using a combination of time-resolved photoluminescence, transmission electron microscopy, X-ray diffraction and spectroscopy, Raman and infrared spectroscopy, as well as ultrafast pump-probe methods. Computational studies based on state-of-the-art first-principles open quantum dynamics method are exploring the scattering processes affecting electron spin lifetime to guide and corroborate experimental studies, which is critical for addressing the complex and challenging issues proposed. 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.