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Diffusion Raman électronique dans les cuprates supraconducteurs

Abstract : The focus of this study is the high T$_c$ superconducting
cuprates. Our experimental tool is inelastic light scattering or
Raman scattering by electronic excitations. Through the use of
selection rules, Raman scattering is able to probe low energy
elementary excitation in different parts of the Fermi surface. The
experimental study was performed on single crystals of
YBa$_2$Cu$_3$O$_{7-\delta}$ and HgBa$_2$CuO$_{4+\delta}$ which
have been studied as a function of the number of carrier or
doping. In the optimally doped regime, our results are consistent
with a superconducting gap of d-wave symmetry. However, in the
superconducting state, we find a second energy scale which is not
directly related to the supercondcuting gap. We show that this
second energy scale is directly linked to a magnetic triplet
excitation observed by inelastic neutron scattering. In the
underdoped regime, we observe an anisotropic suppression of the
Raman response both in the superconducting and normal states. We
interpret this suppression as a signature of a pseudogap in the
charge reponse of the system. Our result are compatible with
models in which the pseudogap result from strong interactions
which compete with superconductivity. We propose a simple model
where the pseudogap is due to antiferromagnetic fluctuations which
grow in strength as we approach the insulating antiferromagnetic state at zero doping.
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Contributor : Yann Gallais <>
Submitted on : Monday, January 9, 2006 - 10:29:54 PM
Last modification on : Monday, December 14, 2020 - 9:48:47 AM
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  • HAL Id : tel-00011331, version 1


Yann Gallais. Diffusion Raman électronique dans les cuprates supraconducteurs. Supraconductivité [cond-mat.supr-con]. Université Pierre et Marie Curie - Paris VI, 2003. Français. ⟨tel-00011331⟩



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