Dynamical Screening of Local Spin Moments at Metal-Molecule Interfaces

TL;DR

This paper investigates how quantum fluctuations and dynamical screening at metal-molecule interfaces affect the local spin moments in transition-metal phthalocyanines, revealing significant quenching effects relevant for spintronics.

Contribution

It provides a systematic analysis of dynamical screening effects on local spin moments using density functional theory and Anderson's Impurity Model, highlighting the role of quantum fluctuations.

Findings

Orbital-dependent hybridization causes strong charge and spin fluctuations.

Screening significantly reduces or quenches local spin moments.

Quantum fluctuations influence measurements in molecular spintronic devices.

Abstract

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.