Scientists have theorized that organometallic halide perovskites are so promising due to a highly controversial mechanism called the Rashba effect. Scientists at the U.S. Department of Energy's Ames Laboratory have now experimentally proven the existence of the effect in bulk perovskites, using short microwave bursts of light to both produce and then record a rhythm, much like music, of the quantum coupled motion of atoms and electrons in these materials.
Research thus far hypothesized that the materials' extraordinary electronic, magnetic and optical properties are related to the Rashba effect, a mechanism that controls the magnetic and electronic structure and charge carrier lifetimes. But despite intense study and debate, conclusive evidence of Rashba effects in bulk organometallic halide perovskites, used in the most efficient perovskite solar cells, remained highly elusive.
'Our discovery settles the debate of the presence of Rashba effects: They do exist in bulk metal halide perovskite materials.' said Jigang Wang, senior scientist at Ames Laboratory and professor of physics at Iowa State University. 'By steering quantum motions of atoms and electrons to engineer Rashba split bands, we achieve a significant leap forward for the fundamental discovery of the effect which had been hidden by random local fluctuations, and also open exciting opportunities for spintronic and photovoltaic applications based on quantum control of perovskite materials.'
Wang and his collaborators at Ames Laboratory and Iowa State University Department of Physics and Astronomy were responsible for terahertz quantum beat spectroscopy, model building, and density functional theoretical simulations. High quality perovskite materials were provided by the University of Toledo. Phonon spectra simulations were performed at the University of Science and Technology of China.
