  Employing the spin degree of freedom of charge carriers offers the
possibility to extend the functionality of conventional electronic devices,
while colloidal chemistry can be used to synthesize inexpensive and tuneable
nanomaterials. In order to benefit from both concepts, Rashba spin-orbit
interaction has been investigated in colloidal lead sulphide nanosheets by
electrical measurements on the circular photo-galvanic effect. Lead sulphide
nanosheets possess rock salt crystal structure, which is centrosymmetric. The
symmetry can be broken by quantum confinement, asymmetric vertical interfaces
and a gate electric field leading to Rashba-type band splitting in momentum
space at the M points, which results in an unconventional selection mechanism
for the excitation of the carriers. The effect, which is supported by
simulations of the band structure using density functional theory, can be tuned
by the gate electric field and by the thickness of the sheets. Spin-related
electrical transport phenomena in colloidal materials open a promising pathway
towards future inexpensive spintronic devices.
