Multiferroic band structure at the monolayer Fe/BaTiO₃ interface

In this work, we study the electronic structure of the multiferroic behavior that has been predicted and observed at the interface of Fe and BaTiO₃ (BTO). To examine the influence of Fe on the BTO electronic structure, we synthesize and measure the band structure of monolayer Fe-BTO interfaces. We observe a two-dimensional electron gas (2DEG) that emerges at the interface of Fe and BTO. This electronic structure is measured using a facility developed on the floor of the National Synchrotron Light Source II (NSLS-II), which combines an oxide MBE growth chamber and a UHV suitcase for sample transfer to an angle-resolved photoemission spectrometer. A comparison of the band structure of the BTO-vacuum interface and the BTO-Fe interface reveals a transfer of spectral weight from the BTO 2DEG to an incoherent band 0.5 eV below the Fermi level. These states are expected to play a role in the tunnel transport from Fe through ferroelectric BTO tunnel barriers.