Theoretical study of electronic structures, magnetic properties, and ultrafast spin manipulation in transition metal adsorbed polycyclic-aromatic-hydrocarbon molecules

We present a first-principles study of the structural, electronic, and magnetic properties of TM(PAH)^0/+ (TM = Fe, Co, Ni; PAH = C₁₀H₈, C₁₆H₁₀, C₂₄H₁₂, C₃₂H₁₄) complexes and explore the laser-induced spin dynamics as well as their stability with respect to various laser parameters. For each complex, the most stable configuration shows that the TM atom prefers to adsorb at the hollow site of the carbon ring with a slight deviation from the center. The electronic structure and spin localization of the complexes are found to be largely affected by the TM type. Driven by various laser pulses, spin-crossover scenarios are achieved in all structures, while spin-transfer between TM and PAH is achieved in Ni(C₁₀H₈), Ni(C₁₆H₁₀), and Ni(C₂₄H₁₂). The influence of the laser energy and chirp on the dynamics is also investigated, providing important information regarding the stability and sensitivity of the dynamical process. All results are believed to reveal the physics nature of the TM-PAH systems, to guide the experimental realization of their ultrafast spin dynamics and thus to promote their applications in future spintronics.