Quantum physicist Talieh Ghiasi has just shown that graphene can host the quantum spin Hall (QSH) effect without any external magnets. In this state, electrons glide effortlessly along the material’s edges while all their spins point the same way.
“Spin is a quantum mechanical property of electrons, which is like a tiny magnet carried by the electrons, pointing up or down,” Ghiasi explains. “We can leverage the spin of electrons to transfer and process information in so-called spintronics devices. Such circuits hold promise for next-generation technologies, including faster and more energy-efficient electronics, quantum computing, and advanced memory devices.”
Integrating Spintronics On-Chip
Until now, researchers needed bulky magnetic fields to detect spin currents in graphene—an approach that would never fit inside everyday electronics.
“In particular, the detection of quantum spin currents in graphene has always required large magnetic fields that are practically impossible to integrate on-chip. Thus, the fact that we are now achieving the quantum spin currents without the need for external magnetic fields opens the path for the future applications of these quantum spintronic devices,” says Ghiasi.
The scientists from the Van der Zant lab were able to bypass the need for external fields by layering the graphene on top of a magnetic material: CrPS₄. This magnetic layer significantly altered the graphene’s electronic properties, giving rise to the QSH effect in graphene. Ghiasi: “We observed that the spin transport in graphene gets modified by the neighbouring CrPS4 such that the flow of electrons in graphene becomes dependent on the electrons’ spin direction.”
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