Time-Resolved Quasiparticle Dynamics in the Spin-Density-Wave State

Chia, Elbert E. M.; Zhu, Jian-Xin; Lee, H. J.; Hur, Namjung; Moreno, N. O.; Averitt, R. D.; Sarrao, J. L.; Taylor, A. J.

Time-Resolved Quasiparticle Dynamics in the Spin-Density-Wave State

Authors

Description

Time-resolved photoinduced reflectivity is measured in the spin-density-wave (SDW) phase using itinerant antiferromagnets UMGa$_{5}$ (M=Ni, Pt). For UNiGa$_{5}$ [$T_{N}$=85 K, $Q$=($π$,$π$,$π$)], the relaxation time $τ$ shows a sharp increase at $T_{N}$ consistent with the opening of a SDW gap. For UPtGa$_{5}$ [$T_{N}$=26 K, $Q$=(0,0,$π$)], no change in $τ$ is observed at $T_{N}$ or at the lowest temperatures. We attribute this to the absence of the SDW gap at the Fermi level, due to a different modulation vector $Q$, which leads to a gapless quasiparticle spectrum. Our results challenge the conventional wisdom that a SDW phase necessarily implies a SDW gap at the Fermi level.
5 pages, 4 figures