Giant room-temperature spin-orbit torque in a bismuthate superconductor

Abstract

The emergence of artificial intelligence and machine-learning-based systems, in conjunction with the pervasive implementation of the internet of things has put a strong emphasis on the energy efficiency of computing. This has triggered research on multiple pathways to improve computing efficiency, spanning 3-D integration of logic and memory as well as new, physics-based pathways including those embracing the electron’s spin degree of freedom, namely spintronics. Concurrently, the proposed integration of superconductivity and spintronics emphasizes complex oxides as a promising platform which in principle can integrate spin current manipulation and high temperature superconductivity within the same complex system. Here, we report giant spin-orbit torque (SOT) discovered in the normal state of a complex oxide superconductor, Ba(Pb,Bi)O3, which provides isotropic and easily manipulated superconducting properties. Using spin-torque ferromagnetic resonance (ST-FMR) and d.c. non-linear Hall measurements, we find a robust SOT efficiency exceeding unity and demonstrate current driven magnetization switching at current densities as low as \(4\times {10}^{5}\text{A}{\text{c}\text{m}}^{-2}\). The hybridized s-p orbital character at the Fermi energy makes this an unexpectedly large value. We postulate the presence of an unconventional SOT generation in bismuthate heterostructures and anticipate our results will trigger further exploration of such complex oxides for the development of superconducting spintronics.