Strontium titanate ($\mathrm{SrTi}{\mathrm{O}}_3$) can exhibit multiple orders, including superconductivity, an antiferrodistortive instability, and ferroelectricity. The cooperation or competition between these orders in samples that undergo all three transitions is of great fundamental interest. Here, we report scanning transmission electron microscopy imaging of the antiferrodistortive and ferroelectric structural distortions in a compressively strained $\mathrm{SrTi}{\mathrm{O}}_3$ film that was previously shown to become superconducting at ∼410 mK. The experiments are complemented by first-principles simulations. Unlike the polar ferroelectric phase, which is suppressed by dopants, the antiferrodistortive order is insensitive to the presence of the free carriers. The single-domain nature of the antiferrodistortive phase excludes any role of antiferrodistortive domain walls in the superconductivity. A previously reported low-temperature resistance anomaly is associated with the ferroelectric transition, not the antiferrodistortive transition.

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• Ferroelasticity
• Ferroelectricity
• Superconductivity
• Superconductors
• Thin films
• Unconventional superconductors