Quantum Microscope Sheds Light on a New Spin‑Transistor Blueprint

When you think of microscopes, you probably picture bright‑field lenses or electron beams. This time the tool was a single‑atom defect—an NV centre in diamond—hunched over a tiny transistor to listen to its magnetic whispers. The result? A vivid picture of how a two‑layer CrSBr crystal can be switched both electrically and magnetically, and why that matters for future computers.

The study was led by Boston College physics professor Brian Zhou, with the graduate‑student‑author Thomas K. M. Graham acting as the voice of the data. Their collaborators included Zdeněk Sofer from the University of Chemistry and Technology in Prague, who grew the ultra‑thin chromium‑sulfur‑bromide (CrSBr) van‑der‑Waals crystal used in the device.

The transistor itself is a bit of a contraption: two layers of CrSBr sit side‑by‑side, each contacted by its own electrode, while a separate gate electrode sits on top. Apply a voltage to the gate and the channel opens—classic CMOS behaviour. Flip the magnetisation of one layer relative to the other, and the device toggles again, this time via a magnetic on/off ratio of roughly 3,000 %.

What really set the experiment apart was the use of scanning NV‑center magnetometry. By sweeping the diamond tip across the chip and tracking the spin resonance of the NV defect, the team could make nanometre‑scale maps of the stray magnetic field. Those maps showed, in real time, how the magnetic domains shifted as the transistor switched.

But the headline‑grabbing numbers didn’t come from fancy imaging alone. The researchers discovered that their CrSBr crystal was operating in a space‑charge‑limited (SCL) conduction regime. In simple terms, the current didn’t flow linearly with voltage; instead it followed a power‑law that amplified the on/off contrast. The electrical on/off ratio they reported was about 1,000,000 %—a ten‑thousand‑fold swing that could make a transistor act like an “instant‑on” switch.

These findings, now published in Physical Review Letters (2026) and posted on arXiv (10.48550/arxiv.2512.03306), hint at a path toward processors that blend logic and non‑volatile memory without the latency penalties of today’s architectures. If you can toggle a device with a tiny magnetic twist as easily as you flick a voltage, you might finally get rid of the dreaded “memory wall.”

Of course, the numbers are still early‑stage laboratory results, and scaling the technology up will take time. Still, the combination of a quantum‑sensing microscope and a van‑der‑Waals spin transistor offers a compelling glimpse of what could be possible when physicists listen closely to the magnetic chatter of a chip.