Momentum dependent ultrafast electron dynamics in antiferromagnetic EuFe2As2

TL;DR

This study uses momentum-sensitive time- and angle-resolved photoemission spectroscopy to analyze ultrafast electron and spin dynamics in antiferromagnetic EuFe2As2, revealing different relaxation times and magnetic order reformation times.

Contribution

It demonstrates a method to distinguish single-particle and many-particle dynamics in antiferromagnetic materials using temperature-dependent relaxation times.

Findings

Different relaxation times for holes and electrons related to the spin density wave gap.

Magnetic order reformation occurs at 800 fs, slower than electron-phonon relaxation.

Spin-dependent relaxation phase space influences magnetic dynamics.

Abstract

Employing the momentum-sensitivity of time- and angle-resolved photoemission spectroscopy we demonstrate the analysis of ultrafast single- and many-particle dynamics in antiferromagnetic EuFe2As2. Their separation is based on a temperature-dependent difference of photo-excited hole and electron relaxation times probing the single particle band and the spin density wave gap, respectively. Reformation of the magnetic order occurs at 800 fs, which is four times slower compared to electron-phonon equilibration due to a smaller spin-dependent relaxation phase space.