Abstract
We report the first measurement of ground-state diamagnetism of isolated neutral atoms in an atomic beam. We realize this measurement using magnetic deflection of fringes in a long-baseline matter-wave interferometer. The observed diamagnetic susceptibilities of for barium and for strontium are in good agreement with the theoretical values and correspond to a measured force on the order of . The high force sensitivity also allows us to observe the isotope dependence of the interference visibility due to the nuclear permanent magnetic moment, thereby demonstrating a new method for neutral isotope selection. The universality of the technique allows the magnetism of a wide range of atoms and molecules to be studied in the gas phase.
- Received 23 August 2019
- Revised 6 November 2019
DOI:https://doi.org/10.1103/PhysRevX.10.011014
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Magnetism and quantum mechanics are intimately related: Even the humble refrigerator magnet cannot be understood without electron spins and quantum theory. In the spirit of this link, we use a quantum-mechanical sensor to study atomic diamagnetism, the most ubiquitous form of magnetism in which matter is repelled from regions of high magnetic field. We study this tiny force by applying a magnetic force and watching free-flying atoms shift in response—a modern twist of the Stern-Gerlach experiment. Our new technique is the first to study this effect on single atoms in such a direct way, and we use it to measure the ground-state diamagnetic susceptibility of atomic barium and strontium.
Since the force on a diamagnetic atom is extremely small, we require a sensor with a high resolution to observe the effect. We accomplish this with an atom interferometer, a device that splits and recombines the wave functions of atoms to create sinusoidal fringes in the density of the atomic beam. These spatial fringes can be monitored with nanometer resolution, and their shift in a magnetic force field encodes information about the atom’s diamagnetic properties. The measured shifts agree well with theoretical predictions, and we also show how one can use the sensitivity of the technique to purify neutral isotopes.
The experimental setup is largely independent of the particle species, providing us with a sensitive magnetic probe for everything from atoms to complex molecules to metal clusters. Future experiments will explore ground- and excited-state magnetism in molecules, including phenomena related to photoswitching.