Acoustic and optical phonon dynamics from femtosecond time-resolved optical spectroscopy of superconducting iron pnictide Ca(Fe_0.944Co_0.056)_2As_2

Abstract

We report temperature evolution of coherently excited acoustic and optical phonon dynamics in superconducting iron pnictide single crystal Ca(Fe_0.944Co_0.056)_2As_2 across the spin density wave transition at T_SDW ~ 85 K and superconducting transition at T_SC ~20 K. Strain pulse propagation model applied to the generation of the acoustic phonons yields the temperature dependence of the optical constants, and longitudinal and transverse sound velocities in the temperature range of 3.1 K to 300 K. The frequency and dephasing times of the phonons show anomalous temperature dependence below T_SC indicating a coupling of these low energy excitations with the Cooper-pair quasiparticles. A maximum in the amplitude of the acoustic modes at T ~ 170 is seen, attributed to spin fluctuations and strong spin-lattice coupling before T_SDW.

6 pages, 4 figures (revised manuscript)

References in corpus (7)

• Theory of Electron Nematic Order in LaOFeAs
• The electronic phase diagram of the LaO1-xFxFeAs superconductor
• Phase transitions in LaFeAsO: structural, magnetic, elastic, and transport properties, heat capacity and Mossbauer spectra
• Probing superconducting energy gap from infrared spectroscopy on a Ba${}_{0.6}$K${}_{0.4}$Fe${}_2$As${}_2$ single crystal with T${}_c$=37 K
• Electron-phonon coupling and charge gap in spin-density-wave iron-pnictides from quasiparticle relaxation dynamics
• Superconductivity-induced optical anomaly in an iron arsenide
• The role of striction at magnetic and structural transitions in iron-pnictides

Cited by in corpus (1)

• Ultrafast quasiparticle dynamics in superconducting iron pnictide CaFe1.89Co0.11As2