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Disorder and transport in cuprates: weak localization and magnetic contributions
No full textURL: http://www-spht.cea.fr/articles/s01/003 Désordre et transport dans les cuprates : localisation faible et contributions magnétiquesWe report resistivity measurements in underdoped YBaCuOand overdoped TlBaCuO single crystals in which the concentration of defects in the CuO planes is controlled by electron irradiation. Low upturns of the resistivity are observed in both cases for large defect content. In the Tl compound the decrease of conductivity scales as expected from weak localization theory. On the contrary in YBaCuO the much larger low T contribution to the resistivity is proportional to the defect content and might then be associated to a Kondo like spin flip scattering term. This would be consistent with the results on the magnetic properties induced by spinless defects
High-field studies of superconducting fluctuations in high-Tc cuprates : Evidence for a small gap distinct from the large pseudogap
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Reply to "comment on 'high- field studies of superconducting fluctuations in high-t-c cuprates: Evidence for a small gap distinct from the large pseudogap
No full textInternational audienceThe experimental investigations done in our paper [Phys. Rev. B 84, 014522 (2011)] allowed us to establish that the superconducting fluctuations (SCF) always die out sharply with increasing T. But contrary to the claim in the Comment of Ramallo et al., this sharp cutoff of SCF measured in YBa2Cu2O6+x depends on hole doping and/or disorder. So our data cannot be used to claim a universality of the extended Gaussian Ginzburg-Landau theory proposed by Ramallo et al. Furthermore, to explain quantitatively our data near optimal doping using this model they need to consider that fluctuations in the two CuO2 planes of a bilayer are totally decoupled, which is not physically well justified. On the contrary, a consistent interpretation of all our data (paraconductivity, Nernst effect, and magnetoresistance) has been done by considering that the coupling between the two layers of the unit cell is dominant at least up to 1.1T(c)
Longitudinal magnetoresistance in Co-doped BaFe 2 As 2 and LiFeAs single crystals: Interplay between spin fluctuations and charge transport in iron pnictides
No full textInternational audienceThe longitudinal in-plane magnetoresistance (LMR) has been measured in different Ba(Fe1−xCox)2As2 single crystals and in LiFeAs. For all these compounds, we find a negative LMR in the paramagnetic phase whose magnitude increases as H 2. We show that this negative LMR can be readily explained in terms of suppression of the spin fluctuations by the magnetic field. In the Co-doped samples, the absolute value of the LMR coefficient is found to decrease with doping content in the paramagnetic phase. The analysis of its T dependence in an itinerant nearly antifer-romagnetic Fermi liquid model evidences that the LMR displays a qualitative change of T variation with increasing Co content. The latter occurs at optimal doping for which the antiferromagnetic ground state is suppressed. The same type of analysis for the negative LMR measured in LiFeAs suggests that this compound is on the verge of magnetism
Influence of electron irradiation defects on the transport properties of cuprates
No full textURL: http://www-drecam.cea.fr/spec/articles/s02/074/International audienc
Respective influences of pair breaking and phase fluctuations in disordered high Tc superconductors
No full text5 pages, 4 figuresElectron irradiation has been used to introduce point defects in a controlled way in the CuO2 planes of underdoped and optimally doped YBCO. This technique allows us to perform very accurate measurements of Tc and of the residual resistivity in a wide range of defect contents xd down to Tc=0. The Tc decrease does not follow the variation expected from pair breaking theories. The evolutions of Tc and of the transition width with xd emphasize the importance of phase fluctuations, at least for the highly damaged regime. These results open new questions about the evolution of the defect induced Tc depression over the phase diagram of the cuprate
High- field studies of superconducting fluctuations in high-Tc cuprates: Evidence for a small gap distinct from the large pseudogap
No full textInternational audienc
Respective influences of pair breaking and phase fluctuations in disordered high Tc superconductors
No full text5 pages, 4 figuresElectron irradiation has been used to introduce point defects in a controlled way in the CuO2 planes of underdoped and optimally doped YBCO. This technique allows us to perform very accurate measurements of Tc and of the residual resistivity in a wide range of defect contents xd down to Tc=0. The Tc decrease does not follow the variation expected from pair breaking theories. The evolutions of Tc and of the transition width with xd emphasize the importance of phase fluctuations, at least for the highly damaged regime. These results open new questions about the evolution of the defect induced Tc depression over the phase diagram of the cuprate
High-field studies of superconducting fluctuations in high-Tc cuprates : Evidence for a small gap distinct from the large pseudogap
No full textInternational audienc
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