Ultrafast Light-Induced Magnetoelectric Effect in van der Waals Magnetic Semiconductor Heterostructures

TL;DR

This study demonstrates ultrafast light-induced magnetoelectric effects in van der Waals heterostructures, revealing a novel mechanism for manipulating magnetization through charge transfer and spin currents.

Contribution

It uncovers a new ultrafast optical mechanism for controlling magnetization in vdW heterostructures via charge transfer and spin currents, differing from traditional photothermal effects.

Findings

Optical excitation in WS₂/CrGeTe₃ bilayers produces an opposite magnetic torque compared to isolated CGT.

Charge transfer across the interface alters magnetic anisotropy, triggering magnetization precession.

Optically-generated spin currents can also induce precessional dynamics in the heterostructure.

Abstract

Atomic-scale heterostructures of van der Waals (vdW) magnets and semiconductors provide a unique environment for exploring magnetic dynamics. In contrast to typical photothermal excitation of precessional magnetization dynamics by a pump laser pulse, we find that ultrafast optical excitation of a WS$_2$/CrGeTe$_3$ (CGT) bilayer produces an opposite sign of magnetic torque compared to an isolated CGT film. Experimental observations by time-resolved magneto-optic Kerr effect (TR-MOKE) and theoretical analysis by density functional theory (DFT) and Landau-Lifshitz-Gilbert (LLG) simulations support a mechanism in which charge transfer of photoexcited carriers across the interface alters the perpendicular magnetic anisotropy, which in turn generates a torque on the magnetic layer to trigger precessional magnetization dynamics. These results provide new avenues for ultrafast manipulation of magnetization in vdW heterostructures with type-II band alignments. Lastly, we show that optically-generated spin currents from WS$_2$ into CGT can also trigger precessional dynamics via angular momentum transfer.