optimization MOT atom number. We vary the MOT detuning Δ, the MOT laser intensity (denoted in the figure as the saturation parameter s0 = I/MI), and the magnetic field gradient ∂B/∂z at the center of the trap projected along the z-axis. Measurements 0 and ∂B/∂z are performed by fixing the detuning and then varying s until the number of atoms is maximized. Each bar represents the optimal number of atoms observed at a given detuning. The captured atomic number fluctuations are estimated from the standard deviation of multiple atomic number measurements for the same MOT parameters. Image source: Physical Review A (2022). DOI: 10.1103/PhysRevA.105.L061101
A team of researchers from the National University of Singapore has developed a custom-made magneto-optical trap (MOT) for cooling indium atoms to near absolute zero. In their paper published in the journal Physical Review A, the team describes tailoring its MOT and its performance when cooling millions of indium atoms.
Over the past few years, scientists have discovered that cooling some atomic gases gives the atoms unique and sometimes useful properties. For example, using this technology, researchers have created quantum sensors and atomic clocks. To cool the atomic gas, scientists use MOTs to cool the gas cloud by applying a spatially varying magnetic field, and then emit laser light to push the atoms out of their ground state. Unfortunately, this technique was found to only work for a few atomic groups on the periodic table . So far, it has only worked on alkaline earth and alkali metal , which means that most of the atoms listed on the table have not been tested at extremely cold temperatures.
In this new effort, the researchers used the transition from the longer-lived metastable state in their MOT, rather than the ground-state transition. This requires modifying it to use only indium atoms.
Once the reconfiguration was complete, the researchers created a cloud of more than 500 million indium-115 atoms in their MOT. They found that their modification allowed the atoms to be cooled to about 1 mK for 12.3 seconds, which is about the same time that the MOT is used to cool other atoms. They believe that the general MOT might also be altered to cool other types of atoms.
The researchers note that they have not yet used their customized MOT to conduct experiments on cold clouds, such as making quantum measurements, but they have no reason to think this is not feasible. They concluded that their technique could be used by other researchers to open new ways of studying atoms in other parts of the periodic table.
More information: Yu Xianquan et al., Magneto-optical trapping of group III atoms, Physical Review A (2022). DOI: 10.1103/PhysRevA.105.L061101
Journal information: Physical Review A
