Exciton decoherence probed by magneto-photoluminescence in halide perovskite bulk single crystals*

Understanding the physics behind the high performance of lead halide perovskite compounds is an urgent objective of photovoltaics research. Due to the existence of large spin-orbit interactions, the investigation of spin properties in these materials has emerged as the primary consideration for using halide perovskites as building blocks in spin-electronic devices. Herein we report on a combined theoretical and experimental effort to probe spin dynamics in halide perovskites using magneto-optical measurements. We perform magneto-photoluminescence measurements of MAPbBr₃ high quality single crystals, observing luminescence intensity suppression and recovery at magnetic fields corresponding to cyclotron frequencies where triplet exciton thermalization is in competition with exciton spin precession into the singlet exciton state. Theoretical modeling of exciton dynamics provides evidence for the existence of an Overhauser effect, arising from spin exchange between the excitonic and nuclear spin systems.