Manuel BIBES - Sagittarius A*, Two-dimensional electron gases at oxide interfaces: a multifunctional platform for condensed matter physics and information technology

Wednesday, October 16, 2024
1:30 p.m. — ConfIV (E244)

Two-dimensional electron gases at oxide interfaces: a multifunctional platform for condensed matter physics and information technology
 

At the interface between quantum oxide materials, structural and/or electronic reconstructions often yield novel 2-dimensional phases with exotic properties. A paradigmatic example is that of the 2-dimensional electron gas (2DEG) forming at the interface of the quantum paraelectric SrTiO₃ and other insulating oxides such as LaAlO₃¹ or AlO_x². This 2DEG displays high electronic mobility, superconductivity³ and Rashba spin-orbit coupling^4,5 (SOC) that are strongly modulable by electrostatic gating, offering opportunities to explore quantum phase transition and for device applications. In particular, the Rashba SOC enables very efficient spin-charge interconversion through the direct and inverse Edelstein and spin Hall effects as we demonstrated in thin film heterostructures^6–8 and nanostructures^9,10. Furthermore, the proximity of SrTiO₃ to a ferroelectric ground state¹¹ can be harnessed to achieve a non-volatile electric-field control of spin-charge interconversion¹². While being non-ferromagnetic, such ferroelectric 2DEGs can then serve as voltage-driven non-volatile sources and detectors of spin currents, thereby emerging as alternatives to ferromagnets in spintronics architectures, albeit with a much reduced switching energy. These functionalities lead to new device concepts for future ultralow power logic-in-memory architectures such as the FESO transistor (ferroelectric spin-orbit)¹³. Beyond SrTiO₃, Rashba 2DEGs can also be generated in another quantum paraelectric, KTaO₃, with enhanced SOC^14,15 and superconducting T_C^16,17. The coexistence of gate-tunable SOC and superconductivity in the same electronic phase position KTaO₃ 2DEGs as an interesting material platform for possible topological superconductivity.

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