The fundamental behavior of hydrogen in relation to the magnetism of nanoscale quantum magnets holds considerable significance within the fields of Kondo physics and spintronics. However, the precise atomic-scale manipulation of molecular spin states and their associated Kondo effects remains a significant challenge. In this study, we theoretically establish that selective hydrogen adsorption can significantly modulate the magnetic characteristics of a single cobalt phthalocyanine (CoPc) molecule adsorbed on an Au(111) substrate. This modulation facilitates the manipulation of the molecular Kondo state, thereby enabling the operation of a Kondo switch. First-principles calculations reveal that the combined influence of reduced structural distortion and elongation of the Co–Au distance upon sufficient hydrogenation leads to a weakened interaction between the adsorbed molecule and the substrate, accompanied by charge redistribution within the molecule. These modifications substantially alter the system's magnetic moment, increasing it from $0{\mu }_{\mathrm{B}}$ to $1.67{\mu }_{\mathrm{B}}$ in the ${\mathrm{H}}_4\text{−}\mathrm{CoPc}/\mathrm{Au}\left(111\right)$ complex. Electronic structure analysis indicates that the spin density localized at the Co center arises from magnetism associated with localized $d$-electrons, whereas the spin density distributed over the Pc ring corresponds to magnetism derived from delocalized $\pi$-electrons. Furthermore, the adsorption of a fifth hydrogen atom atop the central Co ion quenches the molecular magnetism to a nonmagnetic state. The spin-state-switching mechanism observed in the CoPc/Au(111) system serves as a representative model for a potential Kondo switch and provides significant insights for the experimental control and design of collective quantum magnetism in analogous systems.

Close

PrevNext

View figure in article

• Adsorption
• Electronic structure of atoms & molecules
• Kondo effect
• Molecular magnetism
• Quantum transport
• Density functional theory
• First-principles calculations
• Hierarchical equations of motion
• Quantum chemistry methods