Revealing Quantum Behavior in Graphene Devices

Researchers at the National Graphene Institute, University of Manchester, have made progress in quantum electronics with their study on spin injection into graphene. Their findings, published in Communications Materials, contribute to advancements in spintronics and quantum transport.

Innovative Approach to Spintronics

Spin transport electronics, or spintronics, provide an alternative to conventional electronics by using electron spin instead of charge for data transfer and storage. This approach enables energy-efficient, high-speed solutions that address the limitations of classical computation, benefiting both classical and quantum computing technologies.

Led by Dr. Ivan Vera-Marun, the Manchester research team encapsulated monolayer graphene within hexagonal boron nitride, an atomically smooth and insulating 2D material, to maintain its high quality. By structuring the 2D material stack to expose only the edges of the graphene and placing magnetic nanowire electrodes over the stack, they successfully created one-dimensional (1D) contacts.

Quantum Behavior and Ballistic Transport

The study examines the injection process through these 1D contacts at a low temperature of 20 K, showing that electron transport at the interface exhibits quantum behavior. These contacts function as quantum point contacts (QPCs), which are commonly used in quantum nanotechnology and metrology.

This quantum behavior is evidenced by the measurement of quantized conductance through the contacts, indicating that the energy spectrum of electrons transforms into discrete energy subbands upon injection. By adjusting the electron density in the graphene and applying a magnetic field, we visualized these subbands and explored their connection with spin transport.

Dr. Daniel Burrow, Study First Author, National Graphene Institute, University of Manchester

By using magnetic nanowires, these QPCs eliminate the need for a physical constriction within the graphene channel, making their implementation more practical compared to previous methods.

Implications for Quantum Nanotechnology

The device architecture introduced by the Manchester team offers a simple method for developing tunable QPCs in graphene, overcoming fabrication challenges associated with other techniques. The magnetic properties of the nanoscale contacts enable quantized spin injection, opening new possibilities for energy-efficient devices in spin-based quantum nanotechnology.

The successful demonstration of ballistic spin injection is a significant step toward low-power ballistic spintronics. Future research will focus on improving spin transport in graphene by exploiting the quantum injection properties of QPCs.

This study is part of the Horizon Europe Project, "2D Heterostructure Non-volatile Spin Memory Technology" (2DSPIN-TECH), with support from a UKRI grant.

Journal Reference:

Burrow, D., et al. (2025). Spin polarised quantised transport via one-dimensional nanowire-graphene contacts. Communications Materials. doi.org/10.1038/s43246-025-00744-z.