Researchers at the Max Planck Institute of Quantum Optics (MPQ) and the Chinese Academy of Sciences (CAS) have achieved a significant breakthrough by creating and stabilizing a new type of molecule, known as field-linked tetratomic molecules. These “supermolecules” can only exist at ultracold temperatures and have been cooled down to 134 nanokelvin, which is over 3,000 times colder than previously created tetratomic molecules. The research, published in Nature, represents a significant advancement in the study of exotic ultracold matter.
Approximately twenty years ago, physicist John Bohn and colleagues proposed a unique type of binding between polar molecules, where asymmetrically charged molecules can combine in an electric field to form weakly bound “supermolecules.” These polar molecules behave similarly to compass needles inside a hard shell, experiencing a stronger attraction than the Earth’s magnetic field when brought close together. Under specific conditions, polar molecules can form a unique bound state via electrical forces, with a bond length several hundred times longer than normally bound molecules.
The long-range nature of these supermolecules makes them highly sensitive to changes in the electric field, allowing researchers to flexibly vary the shape and size of the molecules with a microwave field.
The creation of these ultracold polyatomic molecules presents new opportunities in areas such as cold chemistry, precision measurements, and quantum information processing. However, their complexity presents a challenge for conventional cooling techniques. Researchers at the MPQ’s “NaK Lab” developed a novel cooling technique for polar molecules using a high-power rotating microwave field, achieving a new low-temperature record.
Following this achievement, researchers were able to observe the signature of binding between these molecules in scattering experiments for the first time, providing indirect evidence of the theoretically predicted exotic constructs. Subsequently, they were able to directly create and stabilize these supermolecules in their experiment, revealing their p-wave symmetry, a crucial feature for the realization of topological quantum materials.
The method used to create these supermolecules is applicable to a wide range of molecular species, allowing for the exploration of a higher variety of ultracold polyatomic molecules. The researchers aim to further cool these bosonic supermolecules to form a Bose-Einstein condensate (BEC), with the potential to transform this BEC into a novel quantum fluid of fermionic molecules by tuning a microwave field.
