Lumped-element resonator design facilitates search for axion dark matter

Dark matter is one of the most sought-after mysteries in the universe, but despite decades of searching, it remains elusive. One of the leading candidates is the axion, a hypothetical particle proposed to solve the strong charge-parity problem in quantum chromodynamics. Because the axion, if it exists, will have an extremely small mass, building a detector capable of measuring it is a challenge.

Kolevatov et al. designed a tabletop lumped-element resonator for axion dark matter searches. Their detector operates at around 250 kilohertz with a quality factor of 2.1×10⁶.

Many axion detectors use cavity resonators to amplify the signals they hope to receive. This is effective at high resonance frequencies, but at lower frequencies, the required size of the cavities makes them impractical. Instead, the researchers designed a lumped-element resonator, which consists of an electric circuit containing a capacitor and an inductor.

“At resonance, the net reactive impedance cancels, so the resonator is limited mainly by internal dissipation — dielectric loss, superconducting surface resistance, and imperfect electrical contacts,” said author Roman Kolevatov. “Our goal was to suppress these losses.”

The biggest challenge in building a lumped-element resonator that operates in the 100 kilohertz range is achieving a high quality factor. Without this, the resonator will be too damped to produce a measurable signal. In addition, a high quality factor directly improves the scan rate in resonant low-mass axion searches. To achieve this, the team used a high-purity aluminum shield, a sapphire dielectric, and a cryogenic environment near 300 millikelvin to maintain superconductivity while minimizing dissipation.

The authors plan to improve their detector response by incorporating tunable components and further improving their materials and design.

“We want to couple this resonator to a superconducting quantum interference device (SQUID),” said Kolevatov. “Because the SQUID is extremely sensitive, this would improve the signal-to-noise ratio substantially.”

Source: “High-Q superconducting lumped-element resonators for low-mass axion searches,” by Roman Kolevatov, Saptarshi Chaudhuri, and Lyman Page, Review of Scientific Instruments (2026). The article can be accessed at https://doi.org/10.1063/5.0311286 .