Emergent two-band conduction at Ti delta-doped LaAlO3/KTaO3 (111) heterointerface

Abstract

Recently, several intriguing interfacial phenomena have been discovered at the KTaO3 (111)-based heterointerfaces, such as the two-dimensional electron gas, superconductivity, anisotropic conductivity, etc. However, the available techniques to systematically manipulate such interfacial states are quite limited. Here, we devise a delta-doping strategy by inserting a sub-nanometer Ti layer with distinct reducibilities to the LaAlO3/KTaO3 (111) interface. In the delta-doped samples, we observe an unforeseen two-band conduction, evidenced by the emergence of a new type of electron carrier with an order-of-magnitude enhancement of mobility (∼1800 cm2V−1s−1) than the original carriers. Moreover, the appearance of the high-mobility carriers causes a sharp transition between the non-Fermi-liquid superconducting state and the Fermi-liquid state with reduced spin–orbit scattering. Further evidence shows that the new type of carriers stems from another in-gap state with a shallower energy level compared to the original carriers. Our study broadens the spectrum of interfacial carrier manipulation by introducing an extra band/channel for carrier conduction, which not only opens up new possibilities in device applications but also shines a light on the underlying physics of interfacial superconductivity.