Gap-dependent quasiparticle dynamics and coherent acoustic phonons in parent iron pnictide CaFe2As2 across the spin density wave phase transition

Abstract

We report ultrafast quasiparticle (QP) dynamics and coherent acoustic phonons in undoped CaFe_2As_2 iron pnictide single crystals exhibiting spin-density wave (SDW) and concurrent structural phase transition at temperature TSDW ~ 165 K using femtosecond time-resolved pump-probe spectroscopy. The contributions in transient differential reflectivity arising from exponentially decaying QP relaxation and oscillatory coherent acoustic phonon mode show large variations in the vicinity of T_SDW. From the temperature-dependence of the QP recombination dynamics in the SDW phase, we evaluate a BCS-like temperature dependent charge gap with its zero-temperature value of ~(1.6+/-0.2)k_BT_SDW, whereas, much above T_SDW, an electron-phonon coupling constant of ~0.13 has been estimated from the linear temperature-dependence of the QP relaxation time. The long-wavelength coherent acoustic phonons with typical time-period of ~100 ps have been analyzed in the light of propagating strain pulse model providing important results for the optical constants, sounds velocity and the elastic modulus of the crystal in the whole temperature range of 3 K to 300 K.

arXiv commentRevised version (to appear as Full Paper in Journal of Physical Society of Japan (2013)); http://jpsj.ipap.jp/link?JPSJ/82/044715/

References in corpus (23)

• Theory of Electron Nematic Order in LaOFeAs
• The electronic phase diagram of the LaO1-xFxFeAs superconductor
• Effects of nematic fluctuations on the elastic properties of iron arsenide superconductors
• Quasiparticle relaxation dynamics in superconductors with different gap structures: theory and experiments on YBa_{2}Cu_{3}O_{7-δ}
• Phase transitions in LaFeAsO: structural, magnetic, elastic, and transport properties, heat capacity and Mossbauer spectra
• Observation of Dirac Cone Electronic Dispersion in BaFe2As2
• The Fermi surface of Ba(1-x)K(x)Fe2As2 and its evolution with doping
• Superconducting gap symmetry of Ba0.6K0.4Fe2As2 studied by angle-resolved photoemission spectroscopy
• Ultrafast transient generation of spin-densitywave order in the normal state of BaFe2As2 driven by coherent lattice vibrations
• Orbital-dependent modifications of electronic structure across magneto-structural transition in BaFe2As2
• Stabilization of an ambient pressure, collapsed tetragonal phase in CaFe2As2 and tuning of the orthorhombic / antiferromagnetic transition temperature by over 70 K by control of nano-precipitates
• Ultrafast transient response and electron-phonon coupling in the iron-pnictide superconductor Ba(Fe(1-x)Co(x))2As2
• Phase diagram of iron-arsenide superconductors Ca(Fe1-xCox)2As2 (0 <= x <= 0.2)
• Quasiparticle relaxation dynamics in spin-density-wave and superconducting SmFeAsO_{1-x}F_{x} single crystals
• Ultrafast spectroscopy of propagating coherent acoustic phonons in GaN/InGaN heterostructures
• Electron-phonon coupling and charge gap in spin-density-wave iron-pnictides from quasiparticle relaxation dynamics
• The role of striction at magnetic and structural transitions in iron-pnictides
• Multiple Gaps and Superfluid Density from Interband Pairing in Iron Oxypnictides
• Gap opening and orbital modification of superconducting FeSe above the structural distortion
• Nonequilibrium Quasiparticle Relaxation Dynamics in Single Crystals of Hole and Electron doped BaFe${}_2$As${}_2$
• Quasiparticle Relaxation Across a Spin Gap in the Itinerant Antiferromagnet UNiGa5
• Measurement of the c-axis optical reflectance of AFe${}_2$As${}_2$ (A=Ba, Sr) single crystals: Evidence of different mechanisms for the formation of two energy gaps
• Electronic structure of CaFe2As2: Contribution of itinerant Fe 3d-states to the Fermi Level

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