N\'eel-Vector Switching and THz Spin-Wave Excitation in Mn$_2$Au due to Femtosecond Spin-Transfer Torques

TL;DR

This paper demonstrates that femtosecond spin-transfer torques generated by ultrafast laser-induced hot-electron currents can rapidly switch antiferromagnetic Mn$_2$Au and excite high-frequency spin waves, advancing ultrafast spintronic control.

Contribution

It introduces a method to control antiferromagnetic order within picoseconds using laser-induced spin-transfer torques, supported by combined transport and spin-model calculations.

Findings

Mn$_2$Au can be switched within a few picoseconds.

High-frequency spin waves up to several THz can be excited.

Femtosecond spin-transfer torques enable ultrafast antiferromagnetic manipulation.

Abstract

Efficient and fast manipulation of antiferromagnets has to date remained a challenging task, hindering their application in spintronic devices. For ultrafast operation of such devices, it is highly desirable to be able to control the antiferromagnetic order within picoseconds - a timescale that is difficult to achieve with electrical circuits. Here, we demonstrate that bursts of spin-polarized hot-electron currents emerging due to laser-induced ultrafast demagnetization are able to efficiently excite spin dynamics in antiferromagnetic Mn$_2$Au by exerting a spin-transfer torque on femtosecond timescales. We combine quantitative superdiffusive transport and atomistic spin-model calculations to describe a spin-valve-type trilayer consisting of Fe$|$Cu$|$Mn$_2$Au. Our results demonstrate that femtosecond spin-transfer torques can switch the Mn$_2$Au layer within a few picoseconds. In addition, we find that spin waves with high frequencies up to several THz can be excited in Mn$_2$Au.