High TC superconductivity in interacting quasi-2D sheets at oxide interfaces

13.10.2020 13:00 – 14:00

High Tc superconductivity has been found at the interface between two insulating oxides, namely, CaCuO2
and SrTiO3, in CaCuO2/SrTiO3 (CCO/STO) heterostructures and superlattices. STEM/EELS measurements
have demonstrated that, in these systems, the hole doping is obtained via oxygen ions uptaking in the Ca
plane of CaCuO2 (CCO) at the interface with the TiO2 plane of SrTiO3 (STO), allowing a Tc of about 40 K in the
heterostructures and about 50 K in the superlattices. A detailed hole doping spatial profile has been
obtained by STEM/EELS at the O K edge: the hole concentration decays rapidly by moving within the CCO
far from the interface with STO, and becomes almost negligible after about two CCO unit cells (two CuO2
planes). So that, the inner CuO2 planes are strongly underdoped and probably undoped and
antiferromagnetic. Basing on these results obtained in CCO/STO systems, we make a comparison among
the superconducting properties of different cuprate-based oxide heterostructures and superlattices.
Throughout this comparison, we propose a phenomenological explanation of the behavior of the Tc by
introducing two kinds of interactions between the superconducting quasi-2D sheets: intra-layer and interlayer
interaction. This interpretation can be extended to standard multilayered high Tc cuprates, which can
be schematized as a sequence of natural interfaces between an insulating block with “infinite layers”
structure, as CCO, and a charge reservoir block.

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Bâtiment: Ecole de Physique

Auditoire Stückelberg

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