Scientists at Ames Laboratory have discovered evidence of the Rashba effect in bulk organometallic halide perovskites by using extremely strong and powerful bursts of light firing at trillions of cycles per second to switch on or synchronize a ‘beat’ of quantum motion within a material sample. They then used a second burst of light to ‘listen’ to the beats, triggering an ultrafast receiver to record images of the oscillating state of matter. Image: US Department of Energy, Ames Laboratory.
Scientists at Ames Laboratory have discovered evidence of the Rashba effect in bulk organometallic halide perovskites by using extremely strong and powerful bursts of light firing at trillions of cycles per second to switch on or synchronize a ‘beat’ of quantum motion within a material sample. They then used a second burst of light to ‘listen’ to the beats, triggering an ultrafast receiver to record images of the oscillating state of matter. Image: US Department of Energy, Ames Laboratory.

Scientists have theorized that organometallic halide perovskites – a class of light-harvesting ‘wonder’ materials with applications in solar cells and quantum electronics – are so promising due to an unseen yet highly controversial mechanism called the Rashba effect.

Now, scientists at the US Department of Energy's Ames Laboratory have experimentally proven the existence of this effect in bulk perovskites. They have done this by 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. They report their findings in a paper in Physical Review Letters.

Organometallic halide perovskites were first introduced in solar cells about a decade ago. Since then, they have been studied intensely for use in light-harvesting, photonics and electronic transport devices, because they deliver highly sought-after optical and dielectric properties. They combine the high energy conversion performance of traditional inorganic photovoltaic devices with the inexpensive material costs and fabrication methods of organic versions.

Research into perovskites has led to the hypothesis that the materials' extraordinary electronic, magnetic and optical properties are related to the Rashba effect, a mechanism that controls magnetic and electronic structure and charge carrier lifetimes. But despite recent intense study and debate, conclusive evidence of Rashba effects in bulk organometallic halide perovskites, which are used in the most efficient perovskite solar cells, remained highly elusive.

Scientists at Ames Laboratory have now uncovered that evidence by using terahertz light – extremely strong and powerful bursts of light firing at trillions of cycles per second – to switch on or synchronize a ‘beat’ of quantum motion within a material sample. They then use a second burst of light to ‘listen’ to the beats, triggering an ultrafast receiver to record images of the oscillating state of matter. This approach overcame the limitations of conventional detection methods, which did not have the resolution or sensitivity to capture the evidence of the Rashba effect hidden in the material's atomic structure.

"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."

This story is adapted from material from Ames Laboratory, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.