Electron Pairing Strength on Crystallographic Orientation*

Recently, it has been shown that superconductivity at the LaAlO₃/SrTiO₃ interface is essentially 1D in nature, and that the pairing mechanism appears to be linked to the boundaries of naturally formed X, Y and Z ferroelastic domains in SrTiO₃ [1]. Here, we investigate the nature of the pairing mechanism in LaAlO₃/SrTiO₃ nanostructures by examining the electron pairing strength with respect to the crystallographic direction. We write 1D, cross-shaped electron waveguides or “nanocrosses” [2] at the LaAlO₃/SrTiO₃ interface using conductive atomic force microscope (c-AFM) lithography. The c-AFM lithography and device geometry together defines the X, Y and Z domain boundaries across the nanocross at low temperatures. A sinusoidal dependence is observed as the nanocross is rotated with respect to the crystallographic direction. This characteristic angular dependence helps to constrain and sharpen our understanding of the pairing mechanism at the interface and the role of ferroelastic domain structure.

[1] Y. Pai et al., Physical review letters 120 (14), 147001 (2018)
[2] A. Nethwewala et al., Nanoscale Horizons 4, 1194-1201 (2019)