Abstract
The emergence of two-dimensional metallic states at the LaAlO3/SrTiO3 (LAO/STO) heterostructure
interface is known to occur at a critical thickness of four LAO over layers. This insulator-to-metal transition can be explained through the “polar catastrophe” mechanism arising
from the divergence of the electrostatic potential at the LAO surface. Here, we demonstrate
that nanostructuring can be effective in reducing or eliminating this critical thickness. Employing
a modified “polar catastrophe" model, we demonstrate that the nanowire heterostructure
electrostatic potential diverges more rapidly as a function of layer thickness than in a regular
heterostructure. Our first principles calculations indicate that for nanowire heterostructure
geometries a one-dimensional electron gas (1DEG) can be induced, consistent with recent experimental
observations of 1D conductivity in LAO/STO steps. Similar to LAO/STO 2DEGs,
we predict that the 1D charge density will decay laterally within a few unit cells away from
the nanowire; thus providing a mechanism for tuning the carrier behavior between 1D and
2D conductivity. In essence, our work provides insight into the creation and manipulation of
charge density at an oxide heterostructure interface and therefore may be beneficial for future
nanoelectronic devices and for the engineering of novel quantum phases.
