Hydrogen-Induced Bipolar Magnetic Semiconducting Phase in Monolayer GeS

Two-dimensional (2D) group-IV monochalcogenides such as GeS provide a rich platform for exploring defect-mediated magnetism in non-magnetic semiconductors. In this work, we use density functional theory and first-principles-based typical medium dynamical cluster approximation (TMDCA) to uncover how hydrogen adsorption induces bipolar magnetic semiconducting behavior in monolayer GeS. Hydrogen adsorption at the Ge-top and S-top sites generates localized magnetic moments by forming spin-polarized impurity states within the bandgap through strong hybridization among H-1s, Ge-4s/4p, and S-3p orbitals. The Ge-top configuration is energetically favored, stabilizing a local moment of ~0.56 μB. Exchange coupling calculations reveal a stripe-like antiferromagnetic (AFM) ground state at ~2.7 at.% H concentration, which transitions to a ferromagnetic (FM) phase below a critical concentration of ~1.9 at.%. In this FM regime, GeS exhibits a bipolar magnetic semiconductor character, with its spin-up and spin-down states symmetrically straddling the Fermi level. Such a construction enables 100% spin filtration across the pristine band edges of the monolayer. Furthermore, incorporating the effects of Ge vacancies within TMDCA shows that native defects act as shallow acceptors that delocalize these impurity states and suppress the induced magnetism. These results highlight hydrogen functionalization as a robust and tunable route to engineer magnetism in non-magnetic 2D semiconductors, paving the way toward defect-controlled spintronic applications in low-dimensional materials.