Imaging Spin-Split Impurity States in Monolayer Semiconductors*

A two dimensional dilute magnetic semiconductor (2D-DMS) is a state sought after for its important implications for spintronics. It is predicted that this state could be achieved by doping monolayer transition metal dichalcogenides with magnetic dopants. Using scanning tunneling microscopy, we investigate the origins of a 2D-DMS state by probing the local density of states in magnetically doped monolayer dichalcogenide semiconductors. We find sharp features in the spectral maps due to an alignment of impurity states with the Fermi level due to tip-induced band bending (TIBB). By modeling the TIBB and comparing to density functional theory, we find evidence for strongly spin-split states in individual dopants, a necessary precursor to the 2D-DMS state. We also use these signatures to characterize impurity types in these samples, finding evidence for both transition metal subsitutional dopants and dichalcogenide substitutions, which collectively alter the magnetic landscape.