Dipole-Tunneling Model from Asymmetric Domain-Wall Conductivity in LiNbO3 Single Crystals

We investigate here the asymmetric domain-wall conductivity (DWC) of neighboring domain walls (DWs) in z-cut periodically poled LiNbO3 single crystals. Asymmetric domain-wall conductivity is observed by scanning-probe-microscopy-based methods and the DW inclination alpha is measured by Cherenkov second-harmonic-generation microscopy. A generalizable dipole-tunneling current model is proposed to elucidate the phenomenon, which also accounts for DW roughness. Our research provides a valuable perspective on how to influence DWC on the microscopic and macroscopic length scales, and the required nanoscopic insights.