Experimental and Theoretical Studies of Magnetic Circular Dichroism for Chiral Lead Halide Perovskites

Chiral lead halide perovskites (LHPs) exhibit pronounced absorption or transmission circular dichroism (CD), which can be efficiently tuned by externally applied magnetic fields, giving rise to magnetic circular dichroism (MCD). To date, a systematic understanding of natural optical activities (NOAs) and magneto-optical activities (MOAs) in LHPs on an equal footing is still lacking. In this work, a joint experimental and theoretical study is carried out systematically in order to establish a unified picture of CD and MCD via a gyration vector for highly crystalline and solution-processable chiral LHPs. Experimentally, MCD strengths that appear near photoabsorption band edges of the chiral LHPs can be enhanced remarkably with increasing fields up to +/- 1.6 T. The experimental results can be well accounted for by a theory based on excitonic states, material chirality, and field dependence of the gyration vector. Importantly, numerical values of the exciton's g-factor and chirality-induced spin-orbit coupling (SOC) strength can be extracted. Our work suggests that the magnetic field can be an important tool to elucidate the microscopic origin of NOA in chiral LHPs.