Fluence-dependent femtosecond quasiparticle and Eu2+ spin relaxation dynamics in EuFe2(As,P)

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 in EuFe 2 (As,P) 2 the SDW order coexists at low temperature with the SC and Eu 2+ -ferromagnetic order. Increasing the excitation fluence leads to a slow thermal suppression of the Eu 2+ spin order due to the crystal-lattice heating on a nanosecond time scale while the SDW order is suppressed nonthermally on a subpicosecond time scale at a higher fluence.

Ultrafast destruction and recovery of the spin density wave order in iron-based pnictides: A multipulse optical study

“…As noted previously [29] we observe a 2-fold rotational anisotropy of the transient reflectivity with respect to the probe polarization with different orientation in different domains. To measure a single domain dominated response the positions on the sample surface with maximal anisotropy of the response have been chosen for measurements.…”