Inhomogeneous energy landscape in LaAlO₃/SrTiO₃ nanostructures

SrTiO₃-based heterointerfaces exhibit gate-tunable superconductivity, magnetism, and several other properties that can be programmed at nanoscale dimensions using conductive atomic force microscopy (c-AFM). Spatially resolved measurements indicate that intrinsic structural distortions in the SrTiO₃ layer can profoundly influence the transport characteristics. Here, we report the low temperature transport properties of quasi-1D, cross-shaped electron waveguides, "nanocrosses", created at the LaAlO₃/SrTiO₃ interface using c-AFM lithography. Inhomogeneities in the electronic band structure of the four arms are observed that are highly reproducible over several device writing/measurement cycles, provided that the writing is performed at the same location on the sample. A proposed ferroelastic domain configuration near the nanocross can provide a mechanism for the observed inhomogeneities. Our model suggests that the three-dimensional ferroelastic domain structure of SrTiO₃ near the LaAlO₃/SrTiO₃ interface can significantly and reproducibly affect the transport properties of the interface. The nanocross geometry can also serve as a building block for understanding the 1D electron physics of LaAlO₃/SrTiO₃ heterostructures.