Enhanced Superconducting Transition Temperature due to Tetragonal Domains in Two-Dimensionally Doped SrTiO${}_3$

Abstract

Strontium titanate is a low-temperature, non-Bardeen-Cooper-Schrieffer superconductor that superconducts to carrier concentrations lower than in any other system and exhibits avoided ferroelectricity at low temperatures. Neither the mechanism of superconductivity in strontium titanate nor the importance of the structure and dielectric properties for the superconductivity are well understood. We studied the effects of twin structure on superconductivity in a 5.5-nm-thick layer of niobium-doped SrTiO${}_3$ embedded in undoped SrTiO${}_3$. We used a scanning superconducting quantum interference device susceptometer to image the local diamagnetic response of the sample as a function of temperature. We observed regions that exhibited a superconducting transition temperature $T_c$ $\gtrsim$ 10% higher than the temperature at which the sample was fully superconducting. The pattern of these regions varied spatially in a manner characteristic of structural twin domains. Our results emphasize that the anisotropic dielectric properties of SrTiO${}_3$ are important for its superconductivity, and need to be considered in any theory of the mechanism of the superconductivity.

arXiv comment14 pages, 11 figures, Supplemental Information available at http://stanford.edu/group/moler/papers/Noad_STOsuperconductivity_SI.pdf

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• Metallicity and superconductivity in doped strontium titanate
• Two-dimensional superconductivity at the (111)LaAlO${}_3$/SrTiO${}_3$ interface
• Non-linear $IV$ characteristics in two-dimensional superconductors: Berezinskii-Kosterlitz-Thouless physics vs inhomogeneity
• One-Dimensional Nature of Pairing and Superconductivity at the LaAlO${}_3$/SrTiO${}_3$ Interface
• Strain and ferroelectric soft mode induced superconductivity in strontium titanate
• Dynamic multiferroicity of a ferroelectric quantum critical point
• Correlation between Superconductivity, Band Filling and Electron Confinement at the LaAlO${}_3$-SrTiO${}_3$ Interface
• Oscillating paramagnetic Meissner effect and Berezinskii-Kosterlitz-Thouless transition in $B{i}_{2}S{r}_{2}CaC{u}_2{O}_{8+\delta }$ monolayer
• Large-scale modulation in the superconducting properties of thin films due to domains in the $SrTi{O}_3$ substrate
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• Observation of the signatures of sub-resolution defects in two-dimensional superconductors with scanning SQUID
• Inhomogeneous superconductivity and quasilinear magnetoresistance at amorphous LaTiO3/SrTiO3 interfaces
• Domain walls in strontium titanate
• Strain-engineered interaction of quantum polar and superconducting phases
• Density-tuned isotherms and dynamic change at phase transition in a gate-controlled superconducting system