High Field determination of superconducting fluctuations in high-Tc cuprates

10th International Conference on Materials and Mechanisms of Superconductivity

Rullier-Albenque, F.^1 ; Alloul, H.^2 ; Colson, D.^1 ; Forget, A.^1

Service de Physique de l'Etat Condensé, Orme des Merisiers, CEA Saclay (CNRS URA 2464), 91191 Gif sur Yvette cedex, France^1

Laboratoire de Physique des Solides, UMR CNRS 8502, Université Paris Sud, 91405 Orsay, France^2

关键词: Fluctuation conductivity;    Gaussian fluctuations;    Magnetoconductance;    Phase fluctuation;    Pseudogap temperature;    Pulsed magnetic fields;    Superconducting fluctuations;    Underdoped samples;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/449/1/012010/pdf
DOI  :  10.1088/1742-6596/449/1/012010

来源: IOP

【 摘 要 】

Large pulsed magnetic fields up to 60 Tesla are used to suppress the contribution of superconducting fluctuations (SCF) to the ab-plane conductivity above Tc in a series of YBa2Cu3O6+x single crystals. The fluctuation conductivity is found to vanish nearly exponentially with temperature, allowing us to determine precisely the field H'c(T) and the temperature T'c above which the SCFs are fully suppressed. T'c is always found much smaller than the pseudogap temperature A careful investigation near optimal doping shows that T'c is higher than the pseudogap T*, which indicates that pseudogap cannot be assigned to preformed pairs. For nearly optimally doped samples, the fluctuation conductivity can be accounted for by gaussian fluctuations following the Ginzburg-Landau scheme. A phase fluctuation contribution might be invoked for the most underdoped samples in a T range which increases when controlled disorder is introduced by electron irradiation. Quantitative analysis of the fluctuating magnetoconductance allows us to determine the critical field Hc2(0) which is found to be quite similar to H'c(0) and to increase with hole doping. Studies of the incidence of disorder on both T'c and T* enable us to propose a three dimensional phase diagram including a disorder axis, which allows to explain most observations done in other cuprate families.