Charge pumping driven by the laser-induced dynamics of the exchange splitting

TL;DR

This paper demonstrates that laser-induced dynamics of exchange splitting in inversion asymmetric ferromagnets generate electric currents, revealing a magnetic inverse Edelstein effect with implications for ultrafast spintronics.

Contribution

It introduces the concept of charge pumping driven by exchange splitting dynamics and provides ab initio calculations for specific bilayer systems, linking theory with experimental THz measurements.

Findings

Electric currents are induced by time-varying exchange splitting after laser excitation.

The effect size varies with magnetization direction in Co/Pt(111) and Mn/W(001).

Ultrafast demagnetization is mainly due to transverse spin fluctuations, not exchange splitting reduction.

Abstract

We show that electric currents are induced in inversion asymmetric ferromagnets if the exchange splitting varies in time after excitation by laser pulses. We interpret this phenomenon as the magnetic variant of the inverse Edelstein effect. Based on \textit{ab initio} calculations we determine the size of this effect in Co/Pt(111) and Mn/W(001) magnetic bilayer systems and investigate its dependence on the magnetization direction. The comparison of our theoretical results to experiments measuring the THz signal emitted after laser excitation suggests that ultrafast demagnetization in 3$d$ transition metal ferromagnets is dominated by transverse spin fluctuations rather than by a reduction of the exchange splitting.