An international team, led by researchers from the University of Zurich’s Department of Physics, has used an improved superconducting nanowire single-photon detector (SNSPD) to probe for dark matter particles across a wide mass range below one mega electron volt (MeV). With a sensitivity threshold of about one-tenth the mass of an electron, their work suggests it is now highly unlikely for dark matter particles to exist above this mass. The study was published in Physical Review Letters.
Using the improved superconducting nanowire single-photon detector (SNSPD), researchers are searching for very light dark matter. Image Credit: UZH
About 80% of the universe's mass is believed to be composed of dark matter. However, the exact composition and structure of its particles are largely unknown, presenting a major challenge to physicists. To study this elusive substance, researchers are working to capture photons, or light particles, which are thought to be produced when dark matter particles collide with the visible matter researchers are familiar with.
Most experiments to date have focused on dark matter particles whose masses roughly align with those of known elementary particles. However, if these particles are lighter than an electron, they would likely go undetected by the current standard of liquid xenon-based detectors. While no experiment has yet directly detected dark matter, this is a significant finding; it confirms that the particles do not exist within the specific mass range and interaction strength that has been previously tested.
New Device Sensitive to Lower-Energy Events
An international research group led by Laura Baudis, Titus Neupert, Björn Penning, and Andreas Schilling of the Department of Physics at UZH has successfully explored the possible existence of dark matter particles across a broad mass range below one mega-electron volt (MeV).
This is the first time we’ve been able to search for dark matter particles in such a low mass range, made possible by a new detector technology.
Laura Baudis, Study First Author, University of Zurich
In a 2022 proof-of-concept study, the team evaluated the first SNSPD device designed with high sensitivity to low-energy photons. When a photon hits the nanowire, it causes a slight increase in temperature, leading to an immediate loss of superconductivity. The wire temporarily turns into a normal conductor, and the resulting rise in electrical resistance can then be detected.
Detecting Smallest Dark Matter Particles
The UZH scientists specifically optimized the superconducting nanowire single-photon detector (SNSPD) for dark matter detection. The team replaced the nanowires with superconducting microwires to maximize the device's cross-section and gave it a thin, planar geometry to make it highly sensitive to directional changes. This feature is crucial because scientists assume the Earth passes through a "wind" of dark matter particles; a detector capable of sensing the resulting seasonal directional shifts can effectively filter out background noise and confirm a true dark matter signal.
Further technological improvements to the SNSPD could enable us to detect signals from dark matter particles with even smaller masses. We also want to deploy the system underground, where it will be better shielded from other sources of radiation.
Titus Neupert, Department of Physics, University of Zurich
When it comes to describing dark matter particles with a mass below that of an electron, current models are significantly limited by astrophysical and cosmological constraints.
Journal Reference:
Baudis, L., et al. (2025) First Sub-MeV Dark Matter Search with the QROCODILE Experiment Using Superconducting Nanowire Single-Photon Detectors. Physical Review Letters. doi.org/10.1103/4hb6-f6jl