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

Who: Dr. Julia Mundy, Harvard University
Thursday, September 27, 2018 - 4:00pm
321 Allen Hall

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.