Negative nonlocal resistance in mesoscopic gold Hall bars: Absence of giant spin Hall effect

TL;DR

This study observes negative nonlocal resistance in mesoscopic gold Hall bars, suggesting a quasiballistic transport mechanism and setting an upper limit on the gold spin Hall angle, challenging spin Hall effect explanations.

Contribution

It provides evidence against the giant spin Hall effect in gold and proposes a quasiballistic transport explanation for negative nonlocal resistance.

Findings

Negative nonlocal resistance observed in gold Hall bars.

Classical diffusive model only partially explains results.

Upper limit for gold spin Hall angle is 0.022 at 4.5 K.

Abstract

We report the observation of negative nonlocal resistances in multiterminal mesoscopic gold Hall bar structures whose characteristic dimensions are larger than the electron mean-free path. Our results can only be partially explained by a classical diffusive model of the nonlocal transport, and are not consistent with a recently proposed model based on spin Hall effects. Instead, our analysis suggests that a quasiballistic transport mechanism is responsible for the observed negative nonlocal resistance. Based on the sensitivity of our measurements and the spin Hall effect model, we find an upper limit for the spin Hall angle in gold of 0.022 at 4.5 K.