Femtosecond Coherent Control of Spin with Light in (Ga,Mn)As ferromagnets

TL;DR

This paper predicts a femtosecond-scale collective spin tilt in (Ga,Mn)As ferromagnets induced by nonlinear coherent light excitation, enabling nonthermal magnetization control and explaining recent ultrafast experimental results.

Contribution

It introduces a theoretical model predicting femtosecond spin control via nonlinear coherent photoexcitation in (Ga,Mn)As, a novel mechanism for ultrafast magnetization manipulation.

Findings

Femtosecond collective spin tilt predicted in (Ga,Mn)As.

Nonthermal magnetization control achievable by tuning laser parameters.

Mechanism explains recent ultrafast pump-probe experimental results.

Abstract

Using density matrix equations of motion, we predict a femtosecond collective spin tilt triggered by nonlinear, near--ultraviolet ($\sim$3eV), coherent photoexcitation of (Ga,Mn)As ferromagnetic semiconductors with linearly polarized light. This dynamics results from carrier coherences and nonthermal populations excited in the \{111\} equivalent directions of the Brillouin zone and triggers a subsequent uniform precession. We predict nonthermal magnetization control by tuning the laser frequency and polarization direction. Our mechanism explains recent ultrafast pump--probe experiments.