Large Tuning of Electroresistance in an Electromagnetic Device Structure Based on the Ferromagnetic-Piezoelectric Interface.

The electrical control of the conducting state through phase transition and/or resistivity switching in heterostructures of strongly correlated oxides is at the core of the large on-going research activity of fundamental and applied interest. In an electromechanical device made of a ferromagnetic-piezoelectric heterostructure, we observe an anomalous negative electroresistance of ∼-282% and a significant tuning of the metal-to-insulator transition temperature when an electric field is applied across the piezoelectric. Supported by finite-element simulations, we identify the electric field applied along the conducting bridge of the device as the plausible origin: stretching the underlying piezoelectric substrate gives rise to a lattice distortion of the ferromagnetic manganite overlayer through epitaxial strain.

Probing Quantum Confinement and Electronic Structure at Polar Oxide Interfaces.

Polar discontinuities occurring at interfaces between two materials constitute both a challenge and an opportunity in the study and application of a variety of devices. In order to cure the large electric field occurring in such structures, a reconfiguration of the charge landscape sets in at the interface via chemical modifications, adsorbates, or charge transfer. In the latter case, one may expect a local electronic doping of one material: one example is the two-dimensional electron liquid (2DEL) appearing in SrTiO once covered by a polar LaAlO layer.

Giant oscillating thermopower at oxide interfaces.

Understanding the nature of charge carriers at the LaAlO3/SrTiO3 interface is one of the major open issues in the full comprehension of the charge confinement phenomenon in oxide heterostructures. Here, we investigate thermopower to study the electronic structure in LaAlO3/SrTiO3 at low temperature as a function of gate field. In particular, under large negative gate voltage, corresponding to the strongly depleted charge density regime, thermopower displays high negative values of the order of 10(4)-10(5) μVK(-1), oscillating at regular intervals as a function of the gate voltage.