Adsorption-enhanced spin–orbit coupling of buckled honeycomb silicon

•The buckled silicon structure can be stabilized by atomic adsorption.•Atomic adsorption can enhance the spin–orbit coupling in silicon structures.•Half-saturated buckled silicon with hydrogen is magnetic.

We have studied the electronic structures of quasi-two-dimensional buckled honeycomb silicon (BHS) saturated by atomic hydrogen and fluorine by means of first-principles calculations. The graphene-like hexagonal silicon with chair configurations can be stabilized by atomic hydrogen and fluorine adsorption. Together with a magnetic ground state, large spin–orbit coupling (SOC) of BHS saturated by hydrogen on either side (Semi-H-BHS) indicated by the band splitting of σ bond at Γ point in the Brillouin zone is attributed to the intermixing between the density of states of hydrogen atoms and π bonds of unpassivated Si2 around the Fermi level. The Zeeman spin splitting is most likely caused by the internal electric field induced by asymmetric charge transfer.