Researchers at the Energy Department's National Renewable Energy Laboratory (NREL) discovered a use for perovskites that could push forward the development of quantum computing.
The discovery, made quite accidentally, occurred while the researchers were investigating excitons in perovskites. The sample was illuminated with a short laser pulse whose wavelength was specifically tuned to avoid being absorbed by the sample. Instead, the exposure triggered a strong interaction of light with the perovskite, producing a shifted transition energy known as the optical Stark effect. The effect occurs in semiconductors, but typically can only be observed at extremely low temperatures in very high-quality, high-cost materials. NREL's scientists were able to observe the effect quite readily at room temperature in materials grown using solution processing.
The NREL team used the Stark effect to remove the degeneracy of the excitonic spin states within the perovskite sample. An electron can have either 'up' or 'down' spins, and electrons with opposite spins can occupy the same electronic state. Circularly polarized light can be used to only interact with one of the spin states, shifting its transition energy.
The optical Stark effect can be used to create promising technologies, including the potential to be used as an ultrafast optical switch. In addition, it can be used to control or address individual spin states, which is needed for spin-based quantum computing.
To further develop this discovery, the researchers will need to demonstrate they can control the spin states and address whether the stability problems that have hampered the use of perovskites as solar cells also are a factor in this area.
