Abstract:We report superconductivity in quasi-1D nanostructures created at the LaAlO 3 /SrTiO 3 interface. Nanostructures having line widths w~10 nm are formed from the parent twodimensional electron liquid using conductive atomic force microscope lithography. Nanowire cross-sections are small compared to the superconducting coherence length in LaAlO 3 /SrTiO 3 (w << SC~1 00 nm), placing them in the quasi-1D regime. Broad superconducting transitions with temperature and finite resistances in the superconducting state well below T c ≈200 mK are observed. V-I curves show switching between the superconducting and normal states that are characteristic of superconducting nanowires.The four-terminal resistance in the superconducting state shows an unusual dependence on the current path, varying by as much as an order of magnitude.

The oxide heterostructure LaAlO 3 =SrTiO 3 supports a two-dimensional electron liquid with a variety of competing phases, including magnetism, superconductivity, and weak antilocalization because of Rashba spin-orbit coupling. Further confinement of this two-dimensional electron liquid to the quasi-onedimensional regime can provide insight into the underlying physics of this system and reveal new behavior. Here, we describe magnetotransport experiments on narrow LaAlO 3 =SrTiO 3 structures created by a conductive atomic force microscope lithography technique. Four-terminal local-transport measurements on Hall bar structures about 10 nm wide yield longitudinal resistances that are comparable to the resistance quantum h=e 2 and independent of the channel length. Large nonlocal resistances (as large as 10 4 ) are observed in some but not all structures with separations between current and voltage that are large compared to the two-dimensional mean-free path. The nonlocal transport is strongly suppressed by the onset of superconductivity below about 200 mK. The origin of these anomalous transport signatures is not understood, but may arise from coherent transport defined by strong spin-orbit coupling and/or magnetic interactions.

The hysteretic piezoelectric response in LaAlO3/SrTiO3 heterostructures can provide important insights into the mechanism for interfacial conductance and its metastability under various conditions. We perform piezoresponse force microscopy experiments on 3 unit cell LaAlO3/SrTiO3 heterostructures. A hysteretic piezoresponse is observed under a variety of non-local environmental and driving conditions. The hysteresis is suppressed when either the sample is placed in vacuum or the interface is electrically grounded. We also find the hysteresis can be affected by the presence of ions. A simple physical model related to surface adsorbates is presented to account for the observed phenomena.

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