Resonant Tunneling through a Ferroelectric Domain Wall

Electron transport across a ferroelectric barrier has attracted interest due to the fundamental physics and potential applications. A prototypal example is the ferroelectric tunnel junction (FTJ), made of two metallic electrodes separated by a thin ferroelectric film. It's been shown experimentally that a head-to-head (HTH) ferroelectric domain structure can be formed in a La_1-xSr_xMnO₃(LSMO)/BaTiO₃(BTO)/La_1-xSr_xMnO₃ FTJ with the domain wall parallel to the plane. Using first-principles density-functional calculations we explore electron transport in the LSMO/BTO/LSMO FTJ. We find that the assumed La_1-xSr_xO/TiO₂ termination at both interfaces stabilizes two ferroelectric domains with polarization pointing at each other. The HTH domain wall in the middle of the BTO layer produces a V-shaped electrostatic potential profile, which pushes the conduction band minimum about 0.17 eV below the Fermi energy and forms a two-dimensional electron gas (2DEG) around the domain wall. Our quantum-transport calculations predict an enhanced transmission at special transverse wave vectors k, indicating resonant tunneling through the 2DEG. The microscopic physics of the resonant tunneling is understood from the analysis of real-space scattering states and the local k-dependent density of states.