Electronic subbands in the a-LaAlO$_3$/KTaO$_3$ interface revealed by quantum oscillations in high magnetic fields

TL;DR

This study uses quantum oscillations in high magnetic fields to reveal the complex electronic subband structure of the 2DEG at the a-LaAlO$_3$/KTaO$_3$ interface, showing coexistence of 2D and 3D charge carriers.

Contribution

It provides experimental evidence of multiple 2D subbands and 3D charge carriers at the interface, aligning with theoretical and spectroscopic studies.

Findings

Four 2D subbands with different effective masses identified

Presence of 3D charge carriers with larger effective mass

Good agreement with theoretical and ARPES studies

Abstract

Investigating Shubnikov-de Haas (SdH) oscillations in high magnetic fields, we experimentally infer the electronic band structure of the quasi-two-dimensional electron gas (2DEG) at the ionic-liquid gated amorphous (a)-LaAlO$_3$/KTaO$_3$ interface. The angular dependence of SdH oscillations indicates a 2D confinement of a majority of electrons at the interface. However, additional SdH oscillations with an angle-independent frequency observed at high tilt angles indicate the coexistence of 3D charge carriers extending deep into the KTaO$_3$. The SdH oscillations measured in magnetic fields perpendicular to the interface show four frequencies corresponding to four 2D subbands with different effective masses (0.20 $m_e$ - 0.55 $m_e$). The single-frequency oscillations originating from 3D electrons yields a larger effective mass of $\sim$ 0.70 $m_e$. Overall, the inferred subbands are in good agreement with the theoretical-calculations and angle-resolved photoemission spectroscopy studies on 2DEG at KTaO$_3$ surface.