Unexpected Anisotropy of the Electron and Hole Lande g-Factors in Perovskite CH3NH3PbI3 Polycrystalline Films

In this work, we studied, at low temperature, the coherent evolution of the localized electron and hole spins in a polycrystalline film of CH3NH3PbI3 (MAPI) by using a picosecondphoto-induced Faraday rotation technique in an oblique magnetic field. We observed an unexpected anisotropy for the electron and hole spin. We determined the electron and hole Lande factors when the magnetic field was applied in the plane of the film and perpendicular to the exciting light, denoted as transverse perpendicular to factors, and when the magnetic field was applied perpendicular to the film and parallel to the exciting light, denoted as parallel parallel to factors. We obtained vertical bar g(e,perpendicular to)vertical bar = 2.600 +/- 0.004, vertical bar g(e,parallel to)vertical bar = 1.604 +/- 0.033 for the electron and vertical bar g(h,perpendicular to)vertical bar = 0.406 +/- 0.002, vertical bar g(h,parallel to)vertical bar = 0.299 +/- 0.007 for the hole Possible origins of this anisotropy are discussed herein.