Giant Spin Splitting in Chiral Perovskites Based on Local Electrical Field Engineering

Chiral
hybrid organic–inorganic perovskites (chiral HOIPs)
present potential spintronic and spin-optoelectronic applications
due to their unique spin-related properties. However, the spin physics
in chiral HOIPs has rarely been explored by theoretical studies. Here,
with first-principles calculations, we investigate the spin characteristics
of the Pb-I based chiral HOIPs and propose an effective approach to
significantly increase the spin splitting with a halogen-substituted
chiral molecule. Compared to the value of 13 meV without halogen substitution,
the spin splitting energy can be significantly enhanced to 73, 90,
and 105 meV with F, Cl, and Br substitution, respectively. A k·p model Hamiltonian based on a symmetry
argument reveals that the halogen substitution enhances the local
electric field, inducing distortion of the PbI6 octahedron.
Further calculation demonstrates that halogen substitution can strongly
modify the electrostatic potential surface of the chiral molecules.
This work presents an effective molecular engineering approach to
modulate spin splitting of chiral HOIPs, shedding light on the design
of spintronic materials.