Agenda

Past colloquia and seminars

02
Jun

Granular superconductivity in cuprate-manganite multilayers

General public Thesis defense

We have discovered a highly unusual proximity effect in cuprate/manganite multilayers in which a thin layer (7 nm) of the high Tc superconductor YBa2Cu3O7 (YBCO) is sandwiched between two thicker layers (20 nm) made from the manganites Pr0.5La0.2Ca0.3MnO3 (PLCMO) or Nd1-x(Ca1-ySry)xMnO3 (NCSMO). Contrary to common knowledge that a magnetic field supresses or destroys superconductivity, in these multilayers we find that the magnetic field restores a coherent superconducting response. I will show that at zero magnetic field these multilayers are in an insulator-like granular superconducting state with localised Cooper pairs that is induced by an interfacial coupling proximity with the charge and orbital order of the neighbouring manganite layers (Mn-CO/OO). As this Mn-CO/OO gets suppressed by a large magnetic field towards a ferromagnetic and metallic state, this unusual proximity effect also disappears and a coherent superconducting state is restored in the YBCO layer. I will provide evidence that in particular the domain boundaries of this Mn-CO/OO states play an important role and may act as a template for corresponding grain boundaries of a copper charge density wave that is induced in the YBCO layer where it competes with superconductivity. This result suggests that these heterostructures can serve as a unique platform to control and study the competing interactions between this Cu-CDW and high Tc superconductivity in the cuprates.


When? 02.06.2020 16:00
Where? PER 08 video conférence
Chemin du Musée 3, 1700 Fribourg 
speaker Jarji KHMALADZE
en vue de l'obtention du titre de
Doctor of Philosophy in Physics
Groupe professeur Christian BERNHARD
Contact Département de Physique
Prof. Christian Bernhard
christian.bernhard@unifr.ch
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