Using Interfacial Electric Fields at Domain Walls to Stabilize Novel Ground States

Interfaces between two distinct complex oxide materials can display ground states which diverge greatly from the parent compounds, making them a playground to establish emergent phenomena. Particularly intriguing are the so-called polar interfaces where a diverging electrostatic potential leads to charge transfer. The canonical polar interface between two insulating oxides, LaAlO3/SrTiO3, forms a two-dimensional electron liquid which superconductors at low-temperature and where the conductivity can be manipulated by changing the film surface. Here, I will demonstrate novel functionality at a very different type of polar interface – a charged domain wall in a ferroelectric. Similar to the polar heterointerfaces, the polarization mismatch causes local, diverging electrostatic potential also requiring charge compensation and hence a change in the electronic structure. Combining mesoscale transport, atomic-scale spectroscopy and theory, we demonstrate electric-field control of the transport at such ferroelectric domain walls. In a separate system, I will alternatively demonstrate how the electrostatic potential from the ferroelectric polarization can drive the system to assume a distinct ground state which can be manipulated with an electric field. Combined these systems present charged ferroelectric domain walls as a platform for stabilizing novel functionality.