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  • Open Access

Ballistic Spin Valve in Graphene Realized via Electron Optics

Daniel Burrow1, Oktay Deveci1, Rares Dragomir1, Thomas Thomson2, and Ivan J. Vera-Marun1,*

  • 1Department of Physics and Astronomy, University of Manchester, Manchester M13 9PL, United Kingdom
  • 2Nano-Engineering and Spintronic Technologies (NEST), Department of Computer Science, University of Manchester, Manchester M13 9PL, United Kingdom

  • *Contact author: ivan.veramarun@manchester.ac.uk
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Phys. Rev. X 16, 021029 – Published 7 May, 2026

DOI: https://doi.org/10.1103/nz6m-kb4l

Abstract

Graphene is an ideal platform for supporting ballistic, spin-coherent transport—crucial ingredients for spin-based quantum technologies. Here, we demonstrate a spin-dependent electron-optic mechanism that enables spin-transistor-like control of spin transport in a graphene spin valve, in the absence of spin-orbit coupling in the transport channel. Using transverse magnetic focusing in a high-mobility graphene device, we couple spin and orbital degrees of freedom through charge transfer doping and proximity exchange at ferromagnetic contacts. This coupling allows for gate-tunable modulation of both the amplitude and polarity of the spin signal, reminiscent of the functionality of a Datta-Das spin field-effect transistor. Measurements confirm that spin-coherent ballistic transport is observable up to room temperature. Our results demonstrate an operational principle for spintronic devices based on spin-dependent electron optics in low spin-orbit coupling materials such as graphene.

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Popular Summary

Realizing practical spin-based transistors requires a material that simultaneously supports long-range ballistic electron transport and coherent spin manipulation, conventionally achieved through tunable spin-orbit coupling, a combination of properties that has proven difficult to achieve in a single system. We address this challenge by developing an ultraclean graphene spin valve encapsulated in hexagonal boron nitride, featuring one-dimensional magnetic contacts for spin injection and detection. Transverse magnetic focusing experiments reveal that ballistic electron transport is fundamentally spin dependent in this architecture and can be continuously manipulated using a back-gate voltage. We find that gate tunability arises from spin-dependent electron optics at the graphene-ferromagnet interfaces, where charge-transfer doping and proximity exchange coupling influence spin-polarized electron transport. These results demonstrate a route toward the realization of two-dimensional spintronic devices without the traditional requirement for strong spin-orbit coupling. Our work establishes a platform for achieving the spin coherence necessary for future quantum technologies and energy-efficient electronics.

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Phys. Rev. X 16, 021029– Published 7 May, 2026
  • Received 19 August 2025
  • Revised 23 December 2025
  • Accepted 5 March 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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