Ultrafast non-equilibrium magnon generation and collapse of spin-orbit hybridization gaps in iron

TL;DR

This study investigates ultrafast spin dynamics in iron, revealing that magnon generation occurs rapidly and selectively affects electronic bands, leading to the collapse of spin-orbit hybridization gaps, with distinct longitudinal and transverse spin responses.

Contribution

It provides new insights into non-equilibrium spin excitations and demonstrates ultrafast, band-specific magnon generation affecting spin-orbit hybridization gaps in iron.

Findings

ΔEex remains constant after optical excitation

Transverse spin dynamics are revealed by MLD response

Magnon generation is ultrafast and band-specific

Abstract

We distinguish between longitudinal and transverse spin excitations in the ultrafast response of iron by probing exchange splitting {\Delta}Eex and magnetic linear dichroism (MLD) in time- and angleresolved photoemission. Comparing spin-split partner bands at the Fermi level shows that {\Delta}Eex remains constant upon optical excitation. In contrast, the different MLD response of spin-orbitsplit valence bands reveals non-equilibrium, transverse spin dynamics. Magnon generation in Fe is ultrafast, electronic band specific, and drives the collapse of spin-orbit hybridization gaps.