Gigantic intrinsic orbital Hall effects in weakly spin-orbit coupled metals

TL;DR

This paper demonstrates that metals with weak spin-orbit coupling exhibit gigantic intrinsic orbital Hall effects, with conductivities comparable to or exceeding those of platinum, and discusses implications for spin-charge conversion experiments.

Contribution

The study reveals that weakly spin-orbit coupled metals have extremely large orbital Hall conductivities, expanding the range of materials for spintronic applications.

Findings

Orbital Hall conductivities are on the order of 10^3-10^4 (ħ/e)(Ω·cm)

Spin Hall conductivities are smaller but still sizable, with spin Hall angles around 0.1

Materials with small SOC can exhibit giant orbital Hall effects

Abstract

A recent paper [Go $\textit{et al}$., Phys. Rev. Lett. $\textbf{121}$, 086602 (2018)] proposed that the intrinsic orbital Hall effect (OHE) can emerge from momentum-space orbital texture in centrosymmetric materials. In searching for real materials with strong OHE, we investigate the intrinsic OHE in metals with small spin-orbit coupling (SOC) in face-centered cubic and body-centered cubic structures (Li, Al, V, Cr, Mn, Ni, and Cu). We find that orbital Hall conductivities (OHCs) in these materials are gigantic $\sim 10^3-10^4\ (\hbar/e)(\Omega\cdot\mathrm{cm})^{-1}$, which are comparable or larger than spin Hall conductivity (SHC) of Pt. Although SHCs in these materials are smaller than OHCs due to small SOC, we found that SHCs are still sizable and the spin Hall angles may be of the order of 0.1. We discuss implications on recent spin-charge interconversion experiments on materials having small SOC.