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TT: Fachverband Tiefe Temperaturen

TT 53: Poster Session: Superconductivity 1

TT 53.7: Poster

Mittwoch, 22. März 2017, 15:00–19:00, P2-OG2

Ferroelectric quantum phase transition inside the superconducting dome of Ca doped SrTiO_3−x — •Lin Xiao — II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln — LPEM, ESPCI, 10 Rue Vauquelin, 75005 Paris, France

Ferroelectricity and superconductivity are mutually exclusive. Ferroelectricity implies the alignment of electric dipoles in an insulator, and while superconductivity requires pairing of mobile electrons in a metal. However, recently a number of ’ferroelectric metals’ have emerged during the past few years (See for example Nature Materials 12, 1024 (2013)). By employing a variety of experimental probes (electric conductivity, electric permittivity, Raman spectroscopy, thermal expansion and sound velocity), we find that calcium doped oxygen-reduced SrTiO₃, is the first solid in which ferroelectric-like and superconducting phase transitions occur one after each order.

A variety of superconducting domes have been found in the vicinity of a competing order during the past three decades. In this context, we find evidence for interplay between superconductivity in strontium titanate and a neighboring ferroelectric order. When the ferroelectric order is destroyed by doping, the superconducting critical temperature enhances. This observation may be the first experimental signature of a role played by ferroelectric quantum criticality in the formation of Cooper pairs.