FisMat2017 - Submission - View

Abstract's title: Novel aspects of superconductive fluctuations in different classes of high-Tc superconductors
Submitting author: Alessandro Lascialfari
Affiliation: Università degli studi di Milano
Affiliation Address: Dipartimento di Fisica Via Celoria 16 - 20133 Milano
Country: Italy
Oral presentation/Poster (Author's request): Oral presentation
Other authors and affiliations: uctors A. Lascialfari^1, S. Sanna^2, G. Prando^3, P. Battistoni^1, A. Rigamonti^3 1 Dipartimento di Fisica and INSTM, Università degli Studi di Milano, Milano, Italy 2 Dipartimento di Fisica e Astronomia, Università degli studi di Bologna, Bologna, Italy 3 Dipartimento di Fisica, Università degli Studi di Pavia, Pavia, Italy
Abstract

In this work we recall the phenomenon of the superconducting fluctuations. First, we describe the related diamagnetism above the transition temperature Tc in the framework of the Ginzburg-Landau theory, with particular attention to the case of metallic nanoparticles and the diamagnetic magnetization curves M vs H above Tc. Then the case of the high-temperature superconductors is addressed. For optimally doped compounds (having the highest Tc) the conventional theory works well. At variance, dramatic modifications are detected for underdoped compounds, highlighted by e.g. an upturn field in M(H) curves at constant temperature T→Tc+. It is shown that all the anomalies in M(H) and in the magnetic susceptibility vs temperature, are related to the occurrence above Tof superconducting “islands” lacking long-range coherence because of phase fluctuations in the order parameter. Finally, the case of CaxLa1-xBa1.75-xLa1.25+xCu3O6+y where the hole doping can be obtained by two different channels (oxygen and Ca doping), is analyzed.