Non-local piezoresponse of LaAlO3/SrTiO3 heterostructures

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.