Ultrafast Dynamics of Orbital Angular Momentum of Electrons Induced by Femtosecond Laser Pulses: Generation and Transfer Across Interfaces

TL;DR

This study explores how femtosecond laser pulses induce and transfer orbital angular momentum in electrons across different materials, revealing mechanisms for ultrafast magnetization control and OAM transfer at interfaces.

Contribution

It provides a theoretical analysis of laser-induced electron OAM dynamics in metals and heterostructures, highlighting conditions for effective OAM generation and transfer.

Findings

Circularly polarized pulses induce long-lasting OAM in normal metals.

Interfaces enable demagnetization via OAM contributions.

Optimal laser setups can transfer OAM from ferromagnets to normal metals.

Abstract

The orbital angular momenta (OAM) of electrons play an increasingly important role in ultrafast electron and magnetization dynamics. In this theoretical study, we investigate the electron dynamics induced by femtosecond laser pulses in a normal metal, a ferromagnet, and a ferromagnet/normal metal heterostructure. We analyze the spatio-temporal distributions of the laser-induced OAM and their respective currents. Our findings demonstrate that a circularly polarized laser pulse can induce a sizable and long-lasting OAM component in a normal metal. Furthermore, an interface between a ferromagnet and a normal metal facilitates the demagnetization of the magnet by the OAM contribution to the total magnetization. Finally, to transfer OAM from a ferromagnet into a normal metal, it is advantageous to use a laser setup that induces the desired OAM component in the ferromagnet, but not in the normal metal.