Ultralow-temperature environments (below 1 kelvin, or -272.15 °C) are essential for quantum computation, precision measurement, and quantum matter studies involving large-scale scientific facilities under extreme conditions. Currently, mainstream dilution refrigeration technology for sub-kelvin cooling relies heavily on helium-3. This dependence acts as a key limiting factor for the development of quantum technologies and other fields requiring ultralow-temperature environments.
Now, for the first time, researchers from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences (CAS), the Institute of Theoretical Physics of CAS, and Shanghai Jiao Tong University have introduced a metal-based cooling strategy that does not rely on the globally scarce isotope helium-3. It is expected to provide a self-sufficient, controllable "super refrigerator" that is critical for advancing frontier quantum technologies.
The findings were published in Nature recently.
Helium-3-free solid-state cooling technologies, such as adiabatic demagnetization refrigeration, have long faced a fundamental challenge: The core materials tend to exhibit poor thermal conductivity—much like a "wooden block" that remains cold internally but cannot rapidly dissipate heat. This results in limited cooling power. In contrast, an ideal magnetocaloric material must combine high cooling capacity with rapid heat transport, analogous to the properties of a metal—a key challenge that has remained unresolved until now.
To address this issue, the researchers designed and synthesized a novel three-dimensional alloy. In experiments, this material exhibited a remarkable state known as a metallic spin supersolid, which combines two seemingly contradictory characteristics. It acts as a powerful "heat-absorbing sponge" that uses the magnetocaloric effect to cool down to 106 millikelvin (approximately -273.05 °C), the lowest temperature achieved by a metal magnetocaloric material without helium-3. At the same time, it shows thermal conductivity 50–100 times higher than that of conventional magnetocaloric materials. This combination enables the material to both generate cooling and dissipate heat instantly.
This work marks a paradigm shift in spin supersolid research, moving it from basic research toward practical application.
By addressing the dual challenges of helium-3 dependency and limited cooling power, this study is expected to provide substantial support for advancing quantum technologies and other cutting-edge fields that rely on ultralow-temperature environments.
Schematic Diagram of Metallic Spin Supersolid and Its Magnetic Refrigeration (Image by XU Xitong)
Lattice structure, key magnetic interactions of ECA, and the resulting spin supersolid state with large entropy change and efficient heat transfer. (Image by XU Xitong)