Rational design principles for giant spin Hall effect in 5d-transition metal oxides

Spin Hall effect (SHE), a mechanism by which materials convert a $\mathit{\text{charge}}$ current into a $\mathit{\text{spin}}$ current, invokes interesting physics and promises to empower transformative, energy-efficient memory technology. However, fundamental questions remain about the essential factors that determine SHE. Here we solve this open problem, presenting a comprehensive theory of five $\mathit{\text{foundational}}\mathit{\text{factors}}$ that control the value of intrinsic SHE in transition metal oxides. Arising from our key insight regarding the inherently geometric nature of SHE, we demonstrate that two of these factors are crystal field strength and structural distortions. Moreover, we discover that a new class of materials (anti-perovskites) promises to demonstrate $\mathit{\text{giant}}$ SHE, that is an order of magnitude larger than that reported for any oxide. We derive three other factors that control SHE and demonstrate the nuanced role of electron correlations. Our findings bring deeper insight into the physics driving SHE, and could help enhance, as well as, externally control SHE values.