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.