Long-Range Non-Coulombic Coupling at the LaAlO3/SrTiO3 Interface

The LaAlO₃/SrTiO₃ interface hosts a plethora of gate-tunable electronic phases. Gating of LaAlO₃/SrTiO₃ interfaces is usually assumed to occur electrostatically. However, increasing evidence suggests that non-local interactions can influence and, in some cases, dominate the coupling between applied gate voltages and electronic properties. Here, quasi-1D ballistic electron waveguides are sketched at the LaAlO₃/SrTiO₃ interface as a probe to understand how gate tunability varies as a function of spatial separation. Gate tunability measurements reveal the scaling law to be at odds with the pure electrostatic coupling observed in traditional semiconductor systems. The non-Coulombic gating at the interface is attributed to a long-range nanoelectromechanical coupling between the gate and electron waveguide, possibly mediated by the ferroelastic domains in SrTiO₃. The long-range interactions at the LaAlO₃/SrTiO₃ interface add unexpected richness and complexity to this correlated electron system.