Persistent Orbital Magnetism from Light-Induced Attosecond Charge Migration in Linear Molecules

Laser-driven coherent charge migration is a fundamental process occurring on the attosecond time scale, and it plays a central role in a wide range of chemical and biological phenomena. In this work, we show that linear polyatomic molecules can exhibit light-induced magnetic behavior through the selective excitation of low-lying, optically accessible charge-transfer states that can bear ring currents. Using ultrashort circularly polarized laser pulses, we demonstrate that oriented lithium cyanide undergoes a screw-like helical charge migration, which generates intense, rapidly oscillating magnetic fields on subfemtosecond time scales. Time-resolved electronic current-density maps are employed to visualize the evolving charge flow and to link the helical currents to the underlying π → σ charge-transfer character of the excitation. These results reveal a chemically intuitive mechanism for inducing ultrafast circulating currents in linear polyatomic molecules and establish a route toward engineering molecular magnetism. The present findings open new opportunities for controlling electronic currents and magnetic responses in molecules, with promising implications for light-driven molecular functionality.