Anisotropic Transport at the LaAlO₃/SrTiO₃ Interface Explained by Microscopic Imaging of Channel-Flow over SrTiO₃ Domains

Oxide interfaces, including the LaAlO₃/SrTiO₃ interface, have been a subject of intense interest for over a decade due to their rich physics and potential as low-dimensional nanoelectronic systems. The field has reached the stage where efforts are invested in developing devices. It is critical now to understand the functionalities and limitations of such devices. Recent scanning probe measurements of the LaAlO₃/SrTiO₃ interface have revealed locally enhanced current flow and accumulation of charge along channels related to SrTiO₃ structural domains. These observations raised a key question regarding the role these modulations play in the macroscopic properties of devices. Here we show that the microscopic picture, mapped by scanning superconducting quantum interference device, accounts for a substantial part of the macroscopically measured transport anisotropy. We compared local flux data with transport values, measured simultaneously, over various SrTiO₃ domain configurations. We show a clear relation between maps of local current density over specific domain configurations and the measured anisotropy for the same device. The domains divert the direction of current flow, resulting in a direction-dependent resistance. We also show that the modulation can be significant and that in some cases up to 95% of the current is modulated over the channels. The orientation and distribution of the SrTiO₃ structural domains change between different cooldowns of the same device or when electric fields are applied, affecting the device behavior. Our results, highlight the importance of substrate physics, and in particular, the role of structural domains, in controlling electronic properties of LaAlO₃/SrTiO₃ devices. Furthermore, these results point to new research directions, exploiting the STO domains ability to divert or even carry current.