Enhancing superconductivity in SrTiO<sub>3</sub> films with strain.

Ahadi, Kaveh; Galletti, Luca; Li, Yuntian; Salmani-Rezaie, Salva; Wu, Wangzhou; Stemmer, Susanne · Sci Adv · 2019

basic_science · Level V

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Abstract

The nature of superconductivity in SrTiO<sub>3</sub>, the first oxide superconductor to be discovered, remains a subject of intense debate several decades after its discovery. SrTiO<sub>3</sub> is also an incipient ferroelectric, and several recent theoretical studies have suggested that the two properties may be linked. To investigate whether such a connection exists, we grew strained, epitaxial SrTiO<sub>3</sub> films, which are known to undergo a ferroelectric transition. We show that, for a range of carrier densities, the superconducting transition temperature is enhanced by up to a factor of two compared to unstrained films grown under the same conditions. Moreover, for these films, superconductivity emerges from a resistive state. We discuss the localization behavior in the context of proximity to ferroelectricity. The results point to new opportunities to enhance superconducting transition temperatures in oxide materials.