Researchers at Columbia and Radboud University have created a dipolar sodium–cesium Bose–Einstein condensate that endures for two seconds at about 5 nK above absolute zero. Using two microwave fields as a form of "shielding," the team stabilized molecules against lossy collisions and improved condensate formation compared with a 2023 trial. The long-lived dipolar BEC enables control of long-range, anisotropic interactions and paves the way to exotic phases such as dipolar droplets, self-organized crystals, and dipolar spin liquids, with broader implications for many-body physics and quantum chemistry.
Scientists Create Long-Lived Dipolar Sodium–Cesium Bose–Einstein Condensate Using Microwave Shielding
Fifth State of Matter Makes a Quantum BreakthroughMARK GARLICK/SCIENCE PHOTO LIBRARY - Getty Images
Researchers at Columbia University, in collaboration with Radboud University, have produced a molecular sodium–cesium Bose–Einstein condensate (BEC) that is dipolar and persists for two full seconds — a notably long lifetime for ultracold experiments. The condensate exists at roughly 5 nanoKelvin above absolute zero (absolute zero = −273.15 °C / −459.67 °F), and its dipolar character gives researchers access to long-range, anisotropic interactions that are useful for exploring new many-body quantum phases.
Background
The idea of a Bose–Einstein condensate dates to the mid-1920s, when Satyendra Nath Bose and Albert Einstein predicted that bosonic particles, when cooled to temperatures just fractions of a degree above absolute zero, would occupy a single quantum state and behave collectively. Laboratory BECs were first realized decades later, and subsequent work has pushed temperatures lower, produced molecular condensates, and used BECs as precise probes of quantum phenomena.
How The Team Reached The BEC
To form the sodium–cesium molecular condensate the team applied two microwave fields to the sample. Rather than heating, the microwaves act as a form of "shielding": they protect low-energy molecules from destructive, lossy collisions while allowing higher-energy molecules to be removed, effectively cooling and stabilizing the sample. The group had tested a single-microwave approach in 2023; adding a second microwave field substantially improved the efficiency of crossing the BEC threshold and produced a long-lived dipolar condensate. The results are published in the journal Nature.
"By controlling these dipolar interactions, we hope to create new quantum states and phases of matter," said Ian Stevenson, a Columbia postdoctoral researcher and co-author of the paper.
"We’ve come up with schemes to control interactions, tested these in theory, and implemented them in the experiment. It’s been amazing to see ideas for microwave ‘shielding’ realized in the lab," said Tijs Karman of Radboud University, also a co-author.
Why Dipolar Matters
Dipolar molecules have a permanent electric dipole moment — effectively separated positive and negative ends — which produces long-range, direction-dependent (anisotropic) interactions. This contrasts with the short-range, isotropic interactions typical of many ultracold-atom experiments. The ability to tune and control these dipolar interactions enables experimental access to exotic many-body phenomena, including:
- Dipolar droplets — self-bound collections of dipolar particles
- Self-organized crystal-like phases in optical lattices
- Dipolar spin liquids and other unconventional quantum phases
Implications and Next Steps
Because the sodium–cesium BEC is both dipolar and long-lived, it provides a versatile platform for studying dipolar many-body physics and for precisely controlling molecular interactions — with potential ramifications for quantum chemistry and simulation. Jun Ye, an ultracold-matter scientist at UC Boulder, noted that the ability to finely tune interactions could lead to new insights and control in quantum chemical processes.
The experiment demonstrates how combining molecular formation with microwave-based techniques opens fresh directions for investigating many-body quantum systems and realizing novel quantum phases.
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