Ultrafast dynamics and phonon softening in Fe1+ySe1−xTex single crystals
oleh: C W Luo, I H Wu, P C Cheng, J-Y Lin, K H Wu, T M Uen, J Y Juang, T Kobayashi, Y C Wen, T W Huang, K W Yeh, M K Wu, D A Chareev, O S Volkova, A N Vasiliev
| Format: | Article |
|---|---|
| Diterbitkan: | IOP Publishing 2012-01-01 |
Deskripsi
The ultrafast quasiparticle dynamics of Fe _1+ _y Se _1− _x Te _x single crystals were investigated by dual-color transient reflectivity measurements (Δ R / 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 Δ R / R . Such a small λ demonstrates the unconventional origin of superconductivity in FeSe. Moreover, the temperature-dependent Δ R / 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.