98% directional guiding of spin currents with 90 micrometer relaxation length in bilayer graphene using carrier drift

TL;DR

This paper demonstrates room-temperature control and long-distance guiding of spin currents in bilayer graphene using carrier drift, achieving millimeter-scale relaxation lengths and high directional efficiency, advancing spintronic device capabilities.

Contribution

It introduces a method to tune spin relaxation length and direct spin currents in bilayer graphene via carrier drift, with significant improvements over previous techniques.

Findings

Spin relaxation length can be tuned from 2 to 88 micrometers with a 40 uA current.

Predicted relaxation lengths extend to 320 micrometers at higher currents.

Directional control achieves up to 99.8% spin flow to one side.

Abstract

Electrical control of spin signals and long distance spin transport are major requirements in the field of spin electronics. Here we report the efficient guiding of spin currents at room temperature in high mobility hexagonal boron nitride encapsulated bilayer graphene using carrier drift. Our experiments, together with modelling, show that the spin relaxation length can be tuned from 2 to 88 micrometers when applying a DC current of $\mp$40 uA respectively. Our model predicts that, extending the range up to $\mathrm{I_{dc}}=\mp$150 uA, the spin relaxation length can be tuned from 0.6 to 320 um respectively, indicating that spin relaxation lengths in the millimeter range are within scope in near future with moderate current densities. Our results also show that we are able to direct spin currents on either side of a spin injection contact. 98% of the injected spins flow to the left when $\mathrm{I_{dc}}$= -40 uA and 65% flow to the right when the drift current is reversed. Our model shows that, for $\mathrm{I_{dc}}=\mp$150 uA the numbers reach 99.8% and 95% respectively showing the potential of carrier drift for spin-based logic operations and devices.