Charge Transport at the Interface of the LaAlO3 and SrTiO3
Akhilesh Kr. Singh1, Ming-Yuan Song1, Chi-Sheng Li1, Chia-Ping Su2, Ming-Wen Chu2, Wei-Li Lee1*
1Institute of Physics, Academia Sinica, Taipei, Taiwan
2Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
* Presenter:Wei-Li Lee,
Complex oxide interface has been an extraordinary system to study various exotic physical phenomena and intriguing interface properties. In this talk, we will review our recent results on the investigation of the charge transport at the interface of LaAlO3(LAO) and SrTiO3(STO), where the high quality epitaxial STO and LAO films were grown by oxide MBE facility at Institute of Physics at Academia Sinica. The n-type carriers were found to highly confined at the LAO/STO interface, which becomes superconducting as the temperature drops below about 0.3 K. By rigorous measurements on the superconducting upper critical field anisotropy, we uncovered an intriguing spin-orbit coupled superconducting phase at the LAO/STO interface. With further tuning of the spin-orbit strength by electrical gating, the correlation between the superconductivity and the spin-orbit coupling can be studied and addressed.
In the second part of the talk, we will show the influence of the additional epitaxial STO-capping layer on LAO/STO to the charge transport near the LAO/STO interface. A long-lasting puzzle and challenge is whether a hole-type conduction near the LAO/STO interface is possible. Through careful two-band model fittings to the magneto-transport data, we uncovered the existence of the additional hole-type conduction channel in STO-capped LAO/STO samples. Surprisingly, both the hole-type and electron-type sheet densities increases with increasing gate voltage, which may infer a novel and spatially-separated electron-hole bilayer near the LAO/STO interface.

Keywords: Superconductivity, Spin-orbit coupling, Complex oxide , Oxide interface