Fluence dependent femtosecond quasi-particle and Eu^{2+} -spin relaxation dynamics in EuFe_{2}(As,P)_{2}

TL;DR

This study explores how femtosecond laser pulses affect the relaxation dynamics of quasi-particles and Eu^{2+} spins in EuFe_{2}(As,P)_{2}, revealing coexistence of magnetic and superconducting orders and their different suppression mechanisms.

Contribution

It provides new insights into fluence-dependent ultrafast dynamics and the interplay of magnetic and superconducting orders in EuFe_{2}(As,P)_{2}.

Findings

SDW order coexists with SC and Eu^{2+}-ferromagnetic order at low temperature.

Increasing fluence thermally suppresses Eu^{2+} spin order.

Higher fluence nonthermally suppresses SDW order.

Abstract

We investigated temperature and fluence dependent dynamics of the time resolved optical reflectivity in undoped spin-density-wave (SDW) and doped superconducting (SC) EuFe$_{2}$(As,P)$_{2}$ with emphasis on the ordered Eu$^{2+}$-spin temperature region. The data indicate that the SDW order coexists at low temperature with the SC and Eu$^{2+}$-ferromagnetic order. Increasing the excitation fluence leads to a thermal suppression of the Eu$^{2+}$-spin order due to the crystal-lattice heating while the SDW order is suppressed nonthermally at a higher fluence.