High valley-degeneracy electron gas at double perovskite - strontium titanate interface

Emergent phenomena such as two-dimensional electron gas (2DEG) and interfacial superconductivity and ferromagnetism are generally built on the interface between insulating oxide thin films and substrates, e.g., LaAlO₃/SrTiO₃, where the 2D profiles of these electronic states are precisely confined at the interface of two insulators. Herein we report a high-mobility electron gas state with unusual symmetry at the interface of the Sr₂CrMoO₆/SrTiO₃ (110) heterostructures, the fermiology of which follows the cubic crystallographic symmetry rather than the two-dimensional interface itself, resulting in the identical Shubnikov-de Haas oscillations with applied magnetic field along all the twelve equivalent [110] crystallographic directions of SrTiO₃, distinctly different from the 2D nature of the electron gas reported previously. Neutron diffraction verifies the predicted ferrimagnetic ordering between Cr and Mo moments. This, together with the magnetic hysteresis loops and negative magnetoresistance in low-field region, suggests possible spin polarization of itinerant electrons. Therefore, a quasi-3D profile, high mobility (up to 10⁴ cm² V⁻¹ s⁻¹) and possibly spin polarized electronic state is observed in the double-perovskite-based oxide heterostructures. This finding of the electronic properties in Sr₂CrMoO₆/SrTiO₃ (110) heterostructure expands the knowledge of interfacial physics, as well as shines light on oxide-based electronics and spintronics research.