The ultrafast quasiparticle dynamics of Fe1+ySe 1-xTex single crystals were investigated by dual-color transient reflectivity measurements (ΔR/R) from 4.3 to 290 K. The electron-phonon coupling strength λ (= 0.16-0.01) and the temperature-dependent energy of longitudinal-acoustic phonons were, respectively, obtained from the relaxation time of a fast component and the period of an oscillation component in ΔR/R. Such a small λ demonstrates the unconventional origin of superconductivity in FeSe. Moreover, the temperature-dependent ΔR/R exhibits anomalous changes at T c, 90 K and 230 K, unambiguously revealing the phase transition as well as the phonon softening via the magnetoelastic effect.
|Number of pages||14|
|Journal||New Journal of Physics|
|State||Published - 1 Oct 2012|