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Gap-Dependent Quasiparticle Dynamics and Coherent Acoustic Phonons in CaFe2As2 across Spin Density Wave Phase Transition

Kumar, Sunil and Harnagea, Luminita and Wurmehl, Sabine and Buchner, Bernd and Sood, AK (2013) Gap-Dependent Quasiparticle Dynamics and Coherent Acoustic Phonons in CaFe2As2 across Spin Density Wave Phase Transition. In: JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 82 (4).

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Official URL: http://dx.doi.org/10.7566/JPSJ.82.044715

Abstract

We report ultrafast quasiparticle (QP) dynamics and coherent acoustic phonons in undoped CaFe2As2 iron pnictide single crystals exhibiting spin-density wave (SDW) and concurrent structural phase transition at temperature T-SDW similar to 165K 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 similar to(1.6 perpendicular to 0.2)k(B)T(SDW), whereas, much above T-SDW, an electron-phonon coupling constant of similar to 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 similar to 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 to 300 K.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to the PHYSICAL SOC JAPAN, JAPAN.
Keywords: ultrafast spectroscopy; iron pnictide; spin density wave; quasiparticle dynamics; acoustic phonons
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Depositing User: Francis Jayakanth
Date Deposited: 14 May 2013 07:22
Last Modified: 14 May 2013 07:22
URI: http://eprints.iisc.ac.in/id/eprint/46491

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