Unlocking the Quantum Twist: Graphene Reveals the True Nature of Spin

For decades, spintronics has faced a stubborn roadblock: we could not clearly see how chiral (twisted) materials filter electron spins because the metal electrodes used to measure them created too much quantum interference. We knew the Chirality-Induced Spin Selectivity (CISS) effect existed, but the mechanism was a black box. This study changes the game by stripping away the heavy metals and utilising graphene, allowing us to visualise the spatial distribution of spin for the first time.

The Graphene Lens

The researchers constructed a device using chiral tellurium nanowires paired with graphene electrodes. Unlike traditional metals, graphene has negligible spin-orbit coupling, meaning it acts as a pristine canvas for observing spin without adding noise. Using reflective magnetic circular dichroism, the team achieved what was previously impossible: real-space imaging of spin scattering. The results shattered the prevailing dogma. Instead of acting as a passive 'spin filter'—where spins of opposite orientation pile up at the interface—the device showed spin polarisation with the identical sign in both the nanowire and the graphene electrodes.

Rewriting the Rules

This observation fundamentally alters our understanding of the CISS effect. The data reveals that spin polarisation scales linearly with current amplitude and aligns perfectly with the direction of current flow. If you reverse the chirality of the wire or the direction of the current, the spin orientation flips instantly. Crucially, this is not a localised effect; the spin signal remains coherent and travels for several micrometres into the graphene. We are not witnessing a simple blockade, but a sophisticated scattering mechanism that actively projects spin information across the device.

The Quantum Future

This discovery provides the blueprint for the next generation of low-power electronics. By proving that chiral materials can inject coherent spin polarisation deep into conductive materials like graphene, we unlock a direct path to chirality-based spintronics. This means we can design logic devices that operate with minimal heat generation and high efficiency. Furthermore, the ability to maintain spin coherence over micrometres suggests these materials could serve as the interconnects for future quantum computers, bridging the gap between quantum processing units and the outside world.