Researchers discovered that the perovskites possess two contradictory properties necessary to make spintronic devices work—the electrons’ spin can be easily controlled, and can also maintain the spin direction long enough to transport information, a property known as spin lifetime.
“It’s a device that people always wanted to make, but there are big challenges in finding a material that can be manipulated and, at the same time, have a long spin lifetime,” says Sarah Li, assistant professor in the Department of Physics and Astronomy at the U and lead author of the study. “But for this material, it’s the property of the material itself that satisfies both.”
“With spintronics, not only have you enormously more information, but you’re not limited by the size of the transistor. The limit in size will be the size of the magnetic moment that you can detect, which is much smaller than the size of the transistor nowadays,” says Vardeny.
The potential for this material is enormous, says Vardeny. It could process data faster and increase random-access memory.
Organic-inorganic hybrid perovskites is already famous in scientific circles for being amazingly efficient at converting sunlight into electricity.
“It’s unbelievable. A miracle material,” says Z. Valy Vardeny, distinguished professor in the Department of Physics and Astronomy and co-author of the study, whose lab studies perovskite solar cells. “In just a few years, solar cells based on this material are at 22 percent efficiency. And now it has this spin lifetime property. It’s fantastic.”
Hybrid organic–inorganic perovskites have emerged as a new class of semiconductors that exhibit excellent performance as active layers in photovoltaic solar cells. These compounds are also highly promising materials for the field of spintronics due to their large and tunable spin–orbit coupling, spin-dependent optical selection rules, and their predicted electrically tunable Rashba spin splitting. Here we demonstrate the optical orientation of excitons and optical detection of spin-polarized exciton quantum beating in polycrystalline films of the hybrid perovskite CH3NH3PbClxI3−x. Time-resolved Faraday rotation measurement in zero magnetic field reveals unexpectedly long spin lifetimes exceeding 1 ns at 4 K, despite the large spin–orbit couplings of the heavy lead and iodine atoms. The quantum beating of exciton states in transverse magnetic fields shows two distinct frequencies, corresponding to two g-factors of 2.63 and −0.33, which we assign to electrons and holes, respectively. These results provide a basic picture of the exciton states in hybrid perovskites, and suggest they hold potential for spintronic applications.
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