In a landmark advance for quantum technology and spintronics, researchers at Delft University of Technology have successfully demonstrated quantum spin currents in graphene without the application of external magnetic fields. This groundbreaking achievement, detailed in the prestigious journal Nature Communications, signals a significant leap toward practical quantum devices that promise greater speed and energy efficiency than conventional electronics. By harnessing the intrinsic properties of graphene integrated with a magnetic material, the team has opened a new frontier in the manipulation and control of electron spins within solid-state systems.
At the core of this breakthrough is the quantum spin Hall (QSH) effect, a phenomenon where electrons with opposite spins propagate in opposite directions along the edges of a two-dimensional material without dissipation. Traditionally, realizing the QSH effect in graphene necessitated imposing large external magnetic fields, an approach that presents substantial hurdles for integration into scalable, on-chip electronic architectures. The team at TU Delft has bypassed this limitation by engineering a heterostructure in which graphene is stacked atop the layered magnetic insulator chromium thiophosphate (CrPS₄). This innovative configuration induces spin-dependent transport in graphene purely through proximity effects, eliminating the need for cumbersome external magnetic influences.
Quantum physicist Talieh Ghiasi, who led the experimental efforts, underscores the significance of spin as a quantum mechanical degree of freedom analogous to a tiny magnet carried by electrons. “In spintronics, electron spin—not just charge—is exploited to encode and process information,” Ghiasi explains. The spin Hall effect enables distinct spin channels to flow along separate trajectories, enabling dissipationless spin currents that offer immense potential for quantum information applications. “Our demonstration of a robust QSH effect in graphene without magnetic fields marks a pivotal step toward realizing spin-based quantum circuits compatible with existing semiconductor technologies,” Ghiasi adds.
Integrating such quantum phenomena within a chip-compatible platform ushers in transformative possibilities for nanoscale devices. Conventional methods requiring external magnetic fields are incompatible with the dense environments of electronic circuits, which demand miniaturization and low power consumption. The CrPS₄/graphene heterostructure delivers an intrinsic magnetic exchange interaction that modifies the band structure of graphene, opening a topological bandgap. This alteration enables electrons to traverse graphene’s edges as spin-polarized, topologically protected channels. Crucially, these spin transport pathways are immune to local defects and disorders—features that are indispensable for building reliable quantum devices capable of coherent information transfer.
One of the most remarkable aspects of the observed quantum spin currents is their topological protection. In essence, this protection guarantees that electron spins remain coherent and do not scatter, allowing spin information to traverse distances of tens of micrometers without degradation. Ghiasi emphasizes, “Preserving the spin signal over such macroscopic distances is essential for practical spintronic circuits, which rely on maintaining quantum coherence for efficient operation.” This resilience to imperfection holds promise for scalable technologies where environmental noise and manufacturing variability otherwise undermine performance.
The experimental setup devised by the Van der Zant group involved delicately crafting the graphene–CrPS₄ stack under clean, controlled environments, allowing precise tuning of the interface interactions. Through low-temperature transport measurements, the team detected spin-polarized edge currents emblematic of the QSH effect, confirmed by their quantized conductance signatures and lack of magnetic field dependence. These findings not only validate theoretical predictions about proximity-induced magnetism in graphene but also represent the first unambiguous observation of such behavior without external magnetic fields.
The discovery carries profound implications for the future of quantum computing and advanced memory technologies. By enabling coherent spin currents in a platform as versatile as graphene, device engineers can envision constructing ultrathin, flexible spintronic circuits that drastically surpass the limitations of charge-based electronics. Spin-based qubits with enhanced coherence times and reduced cross-talk become tangible, providing faster, more reliable quantum gates and storage elements intimately integrated on silicon chips.
The technology also aligns with the rising demand for sustainable electronics. Spintronic devices intrinsically dissipate far less power, as information flows via spin orientations rather than electron motion alone. The graphene–CrPS₄ heterostructure exemplifies a path toward ultra-low-energy quantum devices, harmonizing the imperatives of performance and environmental stewardship in next-generation computing paradigm shifts.
Another dimension of this research is the fundamental insight it sheds on the interplay between van der Waals materials and two-dimensional electron systems. By selecting precise magnetic substrates, the researchers can tailor graphene’s electronic topology, opening avenues for engineering bespoke quantum phases. This versatility unlocks a modular approach to quantum materials design, where devices can be stacked layer by layer to combine complementary properties tailored for specific quantum functionalities.
Looking ahead, challenges remain in refining fabrication techniques and ensuring the robustness of spintronic devices under ambient conditions. Yet the current findings chart an encouraging roadmap for integrating quantum spin currents directly into semiconductor technology, bridging the gap between condensed matter physics and real-world applications. This synergy is poised to rejuvenate the field of quantum information science with scalable, high-performance components grounded in emergent quantum phenomena.
In conclusion, the successful observation of quantum spin currents in graphene without external magnetic fields heralds a new era in spintronics and quantum device engineering. The strategic integration of graphene with CrPS₄ has demonstrated a highly controllable, topologically protected spin transport channel, pivotal for the advent of compact, energetic efficient quantum technologies. As the research community builds on these insights, we may soon witness the emergence of quantum computers and memory devices built on the scalable platforms fashioned from two-dimensional materials, reshaping the technological landscape with unprecedented power and versatility.
Subject of Research: Not applicable
Article Title: [Not explicitly provided]
News Publication Date: 24-Jun-2025
Web References:
https://doi.org/10.1038/s41467-025-60377-1
References:
Ghiasi, T. et al. (2025). Observation of quantum spin Hall effect in graphene-based spintronic devices without external magnetic field. Nature Communications. DOI: 10.1038/s41467-025-60377-1
Image Credits: ScienceBrush, Talieh Ghiasi
Keywords:
Spin Hall effect, Quantum Hall effect, Graphene, Spintronics, Quantum information processing, Quantum computing
