High-mobility spin-polarized two-dimensional electron gas at the interface of LaTiO₃/SrTiO₃ (110) heterostructures

Abstract

High-quality antiferromagnetic Mott insulator thin films of LaTiO₃ (LTO) were epitaxially grown onto SrTiO₃ (STO) (110) substrates using the pulsed laser deposition. The LTO/STO heterostructures are not only highly conducting and ferromagnetic, but also show Kondo effect, Shubnikov‒de Haas (SdH) oscillations with a nonzero Berry phase of \pi, and low-field hysteretic negative magnetoresistance (MR). Angle-dependent SdH oscillations and a calculation of the thickness of the interfacial conducting layer indicate the formation of a 4-nm high mobility two-dimensional electron gas (2DEG) layer at the interface. Moreover, an amazingly large low-field negative MR of ∼61.8% is observed at 1.8 K and 200 Oe, which is approximately one to two orders of magnitude larger than those observed in other spin-polarized 2DEG oxide systems. All these results demonstrate that the 2DEG is spin-polarized and the 4-nm interfacial layer is ferromagnetic, which are attributed to the presence of magnetic Ti³⁺ ions due to interfacial oxygen vacancies and the diffusion of La³⁺ ions into the STO substrate. The localized Ti³⁺ magnetic moments couple to high mobility itinerant electrons under magnetic fields, giving rise to the observed low-field MR. Our work demonstrates the great potential of antiferromagnetic titanate oxide interface for designing spin-polarized 2DEG and spintronic devices.

Graphical abstract

Keywords

two-dimensional electron gas / heterostructure / spin polarization / electronic transport / interface

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Declarations

The authors declare that they have no competing interests and there are no conflicts.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant No. 11974155), the Natural Science Foundation of Guangdong Province (Grant No. 2022A1515010583), and Bureau of Education of Guangzhou Municipality (Grant No. 202255464).

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