Large Rashba spin-orbit-coupling for metallic oxide films*

Oxide interface with large Rashba spin-orbit-coupling (SOC) is hopeful material for spintronic applications owing to the remarkable high spin to charge currents conversion, which promises a substantial reduction of power consumption in spintronic devices. Therefore, there has been a lot of effort spent finding oxide semiconductor heterostructures with large Rashba SOC, such as SrTiO₃ and KTaO₃ based interfaces. Furthermore, there have been several reports on Rashba SOC for metallic oxide ultrathin films, such as SrIrO₃ and La_2/3Sr_1/3MnO₃, although Rashba SOC was even smaller for these materials than for semiconductor heterostructures. Here, we discover metallic ultrathin oxides SrNbO₃ with Rashba SOC, which is largest in the values reported for other metallic oxides and is comparable to the value of LaAlO₃/SrTiO₃. Ultrathin films are advantageous over interfaces because information about the electronic structure and local density of states can be directly obtained by using angle-resolved photoemission and scanning tunneling spectroscopy, respectively. It is expected that Rashba SOC of metallic oxides would be further enhanced by breaking the spatial inversion symmetry such as fabricating heterostructures and applying vertical electric field.