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Magnétisme et supraconductivité dans les pnictures de fer étudiés par diffusion Raman

Abstract : The recent discovery of superconductivity in the iron-pnictides has opened a new field of investigation of the electron pairing mechanism giving rise to high critical temperatures. In these systems, magnetism and superconductivity are competing phases, where the doping x destabilizes the magnetic order for the benefit of the superconducting order. A coexistence regime between these two orders is present for a certain range of doping in the compound Ba(Fe1-xCox)2As2, which was studied by inelastic light scattering. We studied the interaction between the structural, magnetic and electronic degrees of freedom. The study of the vibrational excitations in the crystal shows a strong spin-phonon coupling, through the splitting of an in-plane phonon mode which is amplified by the planar anisotropy of magnetic properties, and a strong electron-phonon coupling, via the significant asymmetry of the arsenide phonon mode. The evolution of the electronic continuum across the magnetic and superconducting transitions traduces, on the one hand, the opening of the spin-density-wave gap, and on the other hand, that the superconducting gap has an anisotropic s-wave symmetry. After having observed separately the impact of each magnetic and superconducting transition on Raman responses, we focused on the coexistence regime between both orders. Our results illustrate a competition for the same electronic states at the Fermi level between these two orders, which establish on different parts of the Fermi surface.
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https://tel.archives-ouvertes.fr/tel-00643775
Contributor : Ludivine Chauviere <>
Submitted on : Tuesday, November 22, 2011 - 5:28:38 PM
Last modification on : Monday, November 9, 2020 - 11:35:05 AM
Long-term archiving on: : Thursday, February 23, 2012 - 2:36:05 AM

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  • HAL Id : tel-00643775, version 1

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Ludivine Chauviere. Magnétisme et supraconductivité dans les pnictures de fer étudiés par diffusion Raman. Supraconductivité [cond-mat.supr-con]. Université Paris-Diderot - Paris VII, 2011. Français. ⟨tel-00643775⟩

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