Exploring Graphene/Oxide Hybrid Heterostructures

Hybrid heterostructures, composed of 2D layered materials and perovskite oxides, showcase unexpected physical and chemical properties arising from functionally synergistic interfaces [1]. Specifically, the interfacial interaction between the strongly correlated nature of complex oxides and quantized electronic states of graphene allows for facile modulation of the electromagnetic characteristics that would not have been achievable otherwise.
First, we show that the quantum Hall effect of graphene can be employed as a quantum sensor of the electrochemical state of perovskite oxide. The substantial voltage scaling in the quantum Hall states of graphene [2] can be utilized to monitor the oxygen vacancy concentration in the SrTiO₃ thin film within the graphene/SrTiO₃ hybrid heterostructures [3].
Second, we reveal that the interfacial interaction with a ferromagnetic LaCoO₃ epitaxial thin film effectively lifts the spin degeneracy in graphene [4]. The presentation highlights a substantial spin exchange splitting in graphene, up to several hundreds of meV, which can be adjusted by the gate electric field. The substantial and tunable exchange splitting is attributed to interfacial charge transfer, as the conventional magnetic proximity effect fails to explain the magnitude and adjustability of the observed exchange splitting.
Hybrid heterostructures used as a platform hold the potential to open avenues for unexpected electromagnetic functionalities.

References
[1] Kang et al. Adv. Mater. 31, 1803732 (2019).
[2] Park et al. Nano Lett. 16, 1754 (2016).
[3] Kang et al. Adv. Mater. 29, 1700071 (2017).
[4] Shin et al. Adv. Funct. Mater. 34, 2311287 (2024).