  We demonstrate theoretically that non-chiral perovskite layers can exhibit
circular dichroism (CD) in the absence of a magnetic field and without chiral
activation by chiral molecules. The effect is shown to be due to splitting of
helical excitonic states which can form in structures of orthorhombic or lower
symmetry that exhibit Rashba spin effects. The selective coupling of these
helical exciton states to helical light is shown to give rise to circular
dichroism. Polarization dependent absorption is shown to occur due to the
combined effect of Rashba splitting, in-plane symmetry breaking, and the effect
of the exciton momentum on its fine structure, which takes the form of Zeeman
splitting in an effective magnetic field. We calculate significant CD with an
anisotropy factor of up to 30% in orthorhombic perovskite layers under
off-normal top illumination conditions, raising the possibility of its
observation in non-chiral perovskite structures.
