Extended Data Fig. 4: HAADF image of NNO/STO interface.

(a) HAADF image of NNO/STO interface at room temperature (b) HAADF image of the similar region at low temperature (115 K), (c) out-of-plane parameter of unit cells at the interface. Error bars correspond to the pixel size in the real space HAADF image, that is, the minimum resolved measurement possible, +−0.05 A. At room temperature, a small expansion of ca. 3% is observed for the last STO unit cell, confirming the experimental work by B. Goodge et al [18]. Interestingly, at 115 K, the expansion becomes more pronounced, reaching approximately 6% and resulting in a unit cell c-axis parameter around 4.10 Å at the last STO. This expansion at 115 K aligns remarkably with the ab initio derived value [18]. Moreover, Ti off-centering is evident in the last STO unit cell (uc -1) at both temperatures, with a cation moving toward the interface.