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Article overview
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Gap-dependent quasiparticle dynamics and coherent acoustic phonons in parent iron pnictide CaFe2As2 across the spin density wave phase transition | | Sunil Kumar
; L. Harnagea
; S. Wurmehl
; B. Buchner
; A. K. Sood
; | | Date: |
18 Aug 2012 | | Abstract: | Using femtosecond time-resolved differential reflectivity measurements we
investigate temperature and fluence-dependence of quasiparticle kinetics in
iron pnictide CaFe2As2 single crystals exhibiting a spin density wave (SDW) and
concurrent structural phase transition at T_SDW ~ 165 K. The fluence-dependence
clearly shows that saturation effects dominate the behavior of the transient
reflectivity signal at pump-fluences higher than ~110 mu J/cm2. Using
pump-fluence well in the linear regime, we have analyzed the
temperature-dependence of three-component carrier relaxation dynamics where the
amplitudes and time-constants of the individual relaxation components show
significant changes in the vicinity of T_SDW. In the SDW phase, using
phonon-bottleneck model, temperature-dependence of the fastest electronic
relaxation process yields the zero-temperature charge gap to be
2Delta(0)/k_BT_SDW ~ 1.6pm0.2 whereas, in the normal state, an
electron-phonon coupling constant of ~0.2 has been estimated from the linear
temperature-dependence of the time-constant. Very low-frequency coherent
oscillations with frequency in the gigahertz range are also observed which are
attributed to coherent excitation of an acoustic phonon mode in the crystal.
These measurements of acoustic phonons give the temperature-dependence of
elastic modulus on either side of the phase transition temperature T_SDW. | | Source: | arXiv, 1208.3742 | | Services: | Forum | Review | PDF | Favorites | |
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