Past colloquia and seminars


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