Tunable electron-electron interactions in LaAlO3/SrTiO3 nanostructures
  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. 
Guanglei Cheng, Michelle Tomczyk, Alexandre B. Tacla, Hyungwoo Lee,   Shicheng Lu, Josh P. Veazey, Mengchen Huang, Patrick I...
cond-mat.str-el cond-mat.mes-hall cond-mat.supr-con