High mobility subbands at a correlated oxide interface

The 3d orbitals at the LaAlO₃/SrTiO₃ (LAO/STO) interface host a manifold of correlated phenomena including electron pairing without superconductivity. These electrons are postulated to reside in multiple quantum wells close to the interface, however, the defect structure at the interface often hampers clean transport study at the strong coupling regime in the low-density limit. Here by tailoring the interface design rule, we report an observation of highly mobile subbands at the LAO/STO interface with low field mobility exceeding 30,000 cm²/Vs. Ultra-low field aperiodic quantum oscillations (0-2 T) are present, and a doubling of the oscillation frequency is observed upon back gating. Our results suggest the observed subbands may reside in quasi-1D ferroelastic domain boundaries which host exeptionally light electrons and pairs.