Levitated Micromagnet Spins at 138 Million RPM to Hunt Dark Matter

The takeaway: combining levitation, spinning and extreme cold yields the quietest microscale rotor anyone has measured.

What does the rotor do besides set records?

The most immediate application, demonstrated in the study itself, is pressure sensing inside ultracold vacuum chambers. The authors write: "We can operate a spinning rotor as a cryogenic pressure sensor at T = 4.2 K in a wide range of pressures down to 10⁻⁸ mbar. The lowest operating temperature previously reported for a spinning rotor gauge was 77 K."

That gap matters for quantum technologies, where stray gas molecules collide with and disturb delicate systems. The authors note that few pressure sensors work at 4.2 K or below, and existing ones — such as ionization gauges — are typically low-accuracy devices requiring specific calibrations. A spinning rotor, by contrast, is regarded by metrological institutes as a highly stable and accurate transfer standard for low-pressure measurements.

The takeaway: this rotor can measure vacuum pressure 18 kelvin colder than any spinning-rotor gauge before it, with metrology-grade stability.

Did it find dark matter?

Not yet — and the authors are explicit about that. The team synchronized the rotor with an oscillating magnetic field so it could detect tiny twisting disturbances, a setup suited to axion-like dark matter, one of the leading hypothetical candidates for cold dark matter. The preliminary search covered only a very narrow frequency range and found no axion signatures, but it placed a fresh upper limit on how strongly such particles could interact with electrons.

The authors write: "Our upper limit on the axion-electron coupling gₐₑ is close to the best laboratory-based limits inferred from fifth-force experiments. We emphasize the very preliminary nature of this measurement and related data analysis in the context of axion-like dark matter."

A wider-band search remains future work, with the team aiming to operate at larger coupling and lower dissipation.

The takeaway: no dark matter found, but a competitive new bound on axion-electron coupling from a first-generation experiment.

What comes next?

The roadmap extends well beyond axions. The authors point to precision rotation sensors, gravity sensors, and tests of materials under extreme mechanical stress as near-term uses. Longer term, they write: "Rotors with elongated shape, featuring a large mass quadrupole moment, will enable a wider class of measurements, such as detection of high-frequency gravitational waves, mechanical tests of spontaneous collapse models, and tests of quantumness versus classicality of gravity."

The findings carry the usual caveats of a first demonstration: a single narrow-band dark matter search, one rotor geometry, and performance that the team itself says has many aspects still to optimize. Even so, the rotor's 24-day decay time and metrology-grade pressure sensing already give experimenters a new benchmark.

A millimeter-scale record stood at 38 million rpm; a 60-micrometer sphere now more than triples it.