Spin Hall Effect and Origins of Nonlocal Resistance in Adatom-Decorated Graphene

TL;DR

This study uses exact numerical methods to analyze the spin Hall effect and nonlocal resistance in adatom-decorated graphene, revealing complex dependencies on clustering and temperature, and proposing a new experimental geometry.

Contribution

It provides a detailed numerical analysis of SHE in realistic graphene models, highlighting the influence of adatom clustering and temperature on spin transport properties.

Findings

Large spin Hall angles (~0.1) at zero temperature

Background contributions significantly affect nonlocal resistance measurements

SHE is strongly suppressed at room temperature

Abstract

Recent experiments reporting unexpectedly large spin Hall effect (SHE) in graphene decorated with adatoms have raised a fierce controversy. We apply numerically exact Kubo and Landauer- Buttiker formulas to realistic models of gold-decorated disordered graphene (including adatom clustering) to obtain the spin Hall conductivity and spin Hall angle, as well as the nonlocal resistance as a quantity accessible to experiments. Large spin Hall angles of 0.1 are obtained at zero-temperature, but their dependence on adatom clustering differs from the predictions of semiclassical transport theories. Furthermore, we find multiple background contributions to the nonlocal resistance, some of which are unrelated to SHE or any other spin-dependent origin, as well as a strong suppression of SHE at room temperature. This motivates us to design a multiterminal graphene geometry which suppresses these background contributions and could, therefore, quantify the upper limit for spin current generation in two-dimensional materials.