Conduction isolated at ferroelectric domain walls has garnered substantial attention, due to both fundamental physics considerations, and the possibility of reconfigurable circuitry that such nanoscale functional elements could provide. However, the mechanism of conduction remains under active debate. Here, we present a new mechanism based on the formation of a polarization nucleus and a twisted structure at the domain wall, that does not rely on intrinsically different conduction mechanisms at the wall. Through investigations of I-V curves on a thin (~10 nm) epitaxial film of BiFeO3 (BFO) on (001) SrTiO3, in combination with phase-field modeling, we show that the formation of a twisted nucleus with nonzero curl leads to a field enhancement, which is sufficient to explain the variation in the I-V curves acquired within domains compared with those obtained at the nominally uncharged wall. This new mechanism is universal, suggests that different electronic properties at the domain wall are unnecessary to explain the literature results, and presents an unexpected merging of the dynamics of topological defects with domain wall conduction.
This research was in part sponsored by the Division of Materials Sciences and Engineering, BES, DOE (RKV, SVK). Research was conducted at the Center for Nanophase Materials Sciences, which also provided support (AI) and which is a DOE Office of Science User Facility. NL acknowledges support from the Eugene P. Wigner Fellowship program at Oak Ridge National Lab. X-ray data was collected at the Advanced Photon Source which is a DOE Office of Science User Facility.