New oxide-based two-dimensional electron and hole gases for spin-orbitronics

The discovery of a two-dimensional electron gas (2DEG) at the interface between SrTiO₃ and LaAlO₃ in 2004 significantly expanded the potential of oxide heterostructures. This breakthrough enabled advancements in electronics, quantum physics, and spin-orbitronics by leveraging Rashba spin-orbit coupling (SOC) resulting from built-in broken inversion symmetry. However, key SOC-related properties, such as long spin diffusion length and efficient spin-charge interconversion, are only present in SrTiO₃ 2DEGs at low temperatures. Additionally, the lack of two-dimensional hole gases (2DHGs) in SrTiO₃ remains a major challenge for implementing SOC functionalities in charge-complementary logic architectures.

To address these limitations, we propose investigating two types of inversion-asymmetric polar oxide interfaces: (i) BaSnO₃-based 2DEGs, which exhibit room-temperature mobilities over ten times higher than those of SrTiO₃ 2DEGs, and (ii) SrTiO₃- and KTaO₃-based 2DHGs. Their spin and orbital textures, as well as transport characteristics, will be analyzed using tight-binding band models and Boltzmann calculations.

The samples will be grown with atomic-scale precision using oxide molecular beam epitaxy. Carrier density and mobility of both 2DEGs and 2DHGs will be determined through magnetotransport measurements, while Rashba SOC coefficients will be experimentally quantified and compared with theoretical predictions. To explore superconducting ground states, we will use three-terminal devices to modulate carrier density systematically.

Furthermore, we will fabricate spin transport device structures to quantify spin-charge interconversion efficiency. By integrating both hole- and electron-based spin transport functionalities within a single device, we aim to achieve three-terminal logic device operation, utilizing the spin and charge degrees of freedom in 2D electron and hole gases.