Chinese scientists have directly observed the long-theorized Migdal effect for the first time, marking a major breakthrough in the global quest to detect light dark matter.

The study, led by a research team from the University of Chinese Academy of Sciences (UCAS), was published in Nature on January 15.

The Migdal effect was first proposed in 1939 by Soviet physicist Arkady Migdal. It describes a phenomenon where an atom, jolted by a collision with a neutral particle (such as  dark matter), fails to immediately adjust its electron cloud to the moving nucleus. This "lag" causes the atom to release electrons that can be detected by sensitive instruments. For decades, the effect remained a theoretical prediction.

In modern particle physics, scientists have increasingly recognized that the Migdal effect could provide a crucial pathway to overcome sensitivity limits in the detection for light dark matter, as one of the deepest mysteries in modern physics. However, the lack of direct experimental evidence has long raised doubts about its practical applicability.

Liu Qian, a professor at University of Chinese Academy of Sciences (UCAS) and a member of the research team, told Xinhua the breakthrough was enabled by a newly developed ultra-sensitive detection system combining a micro-pattern gas detector with a pixelated readout chip. The device functions like a "camera" capable of capturing the moment electrons are released during atomic recoil.

In the experiment, a compact deuterium–deuterium generator produced neutrons that bombarded the detector's gas, producing recoiling nuclei and Migdal electrons, leaving a distinctive pair of tracks with a common vertex.

By identifying this unique signature, researchers were able to distinguish "Migdal events" from background signals such as gamma rays and cosmic radiation. The results provided the first direct experimental confirmation of the Migdal effect as predicted by quantum mechanics more than 80 years ago.

This achievement fills a long-standing gap and strengthens the theoretical foundation for Migdal-based dark matter searches, said Yue Qian of the China Dark Matter Experiment (CDEX). He noted that the work also highlights China's growing capabilities in high-precision gas detector technology.

Zheng Yangheng, a professor at UCAS and a core member of the project, told Xinhua the team plans to collaborate with dark matter detection groups to incorporate the findings into the design of next-generation detectors.

"Dark matter holds the key to understanding the origin and evolution of the universe," he said. "Our work brings humanity one step closer in this 'cosmic treasure hunt'."