Tuneable spin injection in high-quality graphene with one-dimensional contacts

TL;DR

This paper demonstrates tunable spin injection in high-quality, fully-encapsulated graphene using one-dimensional contacts, achieving high mobility and long spin diffusion lengths, with controllable spin signals via electrostatic gating.

Contribution

It introduces a novel van der Waals heterostructure with 1D contacts that prevent doping, enabling high-quality graphene spin transport with tunable signals at room and low temperatures.

Findings

High mobility graphene channels with up to 130,000 cm²V⁻¹s⁻¹.

Spin diffusion lengths approaching 20 μm.

Electrostatic gating enhances spin signals by up to an order of magnitude.

Abstract

Spintronics involves the development of low-dimensional electronic systems with potential use in quantum-based computation. In graphene, there has been significant progress in improving spin transport characteristics by encapsulation and reducing impurities, but the influence of standard two-dimensional (2D) tunnel contacts, via pinholes and doping of the graphene channel, remains difficult to eliminate. Here, we report the observation of spin injection and tuneable spin signal in fully-encapsulated graphene, enabled by van der Waals heterostructures with one-dimensional (1D) contacts. This architecture prevents significant doping from the contacts, enabling high-quality graphene channels, currently with mobilities up to 130,000 cm$^2$V$^{-1}$s$^{-1}$ and spin diffusion lengths approaching 20 ${\mu}$m. The nanoscale-wide 1D contacts allow spin injection both at room and at low temperature, with the latter exhibiting efficiency comparable with 2D tunnel contacts. At low temperature, the spin signals can be enhanced by as much as an order of magnitude by electrostatic gating, adding new functionality.