Tunable electron-electron interactions in LaAlO3/SrTiO3 nanostructures

Cheng, Guanglei and Tomczyk, Michelle and Tacla, Alexandre B. and Lee, Hyungwoo and Lu, Shicheng and Veazey, Josh P. and Huang, Mengchen and Irvin, Patrick and Ryu, Sangwoo and Eom, Chang-Beom and Daley, Andrew and Pekker, David and Levy, Jeremy (2016) Tunable electron-electron interactions in LaAlO3/SrTiO3 nanostructures. Physical Review X, 6 (4). 041042. ISSN 2160-3308 (https://doi.org/10.1103/PhysRevX.6.041042)

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The interface between the two complex oxides LaAlO3 and SrTiO3 has remarkable properties that can be locally reconfigured between conducting and insulating states using a conductive atomic force microscope. Prior investigations of "sketched" quantum dot devices revealed a phase in which electrons form pairs, implying a strongly attractive electron-electron interaction. Here, we show that these devices with strong electron-electron interactions can exhibit a gate-tunable transition from a pair-tunneling regime to a single-electron (Andreev bound state) tunneling regime where the interactions become repulsive. The electron-electron interaction sign change is associated with a Lifshitz transition where the dxz and dyz bands start to become occupied. This electronically tunable electron-electron interaction, combined with the nanoscale reconfigurability of this system, provides an interesting starting point towards solid-state quantum simulation.