Dynamical Screening of Local Spin Moments at Metal-Molecule Interfaces

Transition-metal phthalocyanine molecules have attracted considerable interest in the context of spintronics device development due to their amenability to diverse bonding regimes and their intrinsic magnetism. The latter is highly influenced by the quantum fluctuations that arise at the inevitable metal-molecule interface in a device architecture. In this study, we have systematically investigated the dynamical screening effects in phthalocyanine molecules hosting a series of transition-metal ions (Ti, V, Cr, Mn, Fe, Co, and Ni) in contact with the Cu(111) surface. Using comprehensive density functional theory plus Anderson's Impurity Model calculations, we show that the orbital-dependent hybridization and electron correlation together result in strong charge and spin fluctuations. While the instantaneous spin moments of the transition-metal ions are near atomic-like, we find that screening gives rise to considerable lowering or even quenching of these. Our results highlight the importance of quantum fluctuations in metal-contacted molecular devices, which may influence the results obtained from theoretical or experimental probes, depending on their possibly material-dependent characteristic sampling time-scales.

Automated summary

Transition-metal phthalocyanine molecules are important in spintronics device development due to their diverse bonding and intrinsic magnetism, which is influenced by quantum fluctuations at the metal-molecule interface. In this study, the dynamical screening effects in phthalocyanine molecules with various transition-metal ions in contact with Cu(111) surface were systematically investigated. The results show strong charge and spin fluctuations due to orbital-dependent hybridization and electron correlation, leading to significant reduction or suppression of spin moments. This highlights the importance of quantum fluctuations in metal-contacted molecular devices.