Opticalspinsplittinghasattractedsignificantattentionowingtoitspotentialapplicationsinquantuminformationandprecisionmetrology.However,itistypicallysmallandcannotbecontrolledefficiently.Here,weenhancethespinsplittingbytransmittinghigher-orderLaguerre–Gaussian(LG)beamsthroughgraphenemetamaterialslabs.TheinteractionbetweenLGbeamsandmetamaterialresultsinanorbital-angularmomentum-(OAM)dependentspinsplitting.TheupperboundoftheOAM-dependentspinsplittingisfound,whichvarieswiththeincidentOAMandbeamwaist.Moreover,thespinsplittingcanbeflexiblytunedbymodulatingtheFermienergyofthegraphenesheets.Thistunablespinsplittinghaspotentialapplicationsinthedevelopmentofspin-basedapplicationsandthemanipulationofmid-infraredwaves.
